Learn Hardcore Croatian: Večeras idemo pogledati film, a sutra ćemo ići učiti hrvatski. - Tonight we are going to watch a movie, and tomorrow we will go to study Croatian.

In Croatian, the present tense is very commonly used for planned or certain future events, especially when you have a time word like večeras (this evening), sutra (tomorrow), za sat vremena (in an hour), etc.

So Večeras idemo pogledati film literally is This evening we go to watch a film, but it is understood as we are going to watch a film this evening / we’re going to go watch a film this evening.

You could also say Večeras ćemo ići pogledati film, but the simple present idemo sounds more natural and conversational in this context and emphasises a fixed plan.

Why do we have two verbs in idemo pogledati film? Is this like English go see a movie?

Yes, it’s very similar to English go see a movie, go buy bread, etc.

Structure:

idemo = we go / we are going
pogledati = infinitive, to watch / to take a look at (once, completely)
film = a film / the film

In Croatian, ići (to go) often combines with an infinitive to express going somewhere in order to do something:

Idem kupiti kruh. – I’m going (in order) to buy bread.
Idemo popiti kavu. – We’re going to have a coffee.
Idem pogledati film. – I’m going to go watch a film.

So idemo pogledati functions as go (and) watch, just like in English.

What is the difference between pogledati and gledati?

This is an aspect difference (perfective vs. imperfective):

gledati – imperfective: to watch, to be watching, focusing on the ongoing activity or repeated action.
pogledati – perfective: to watch once / to watch through / to take a look, focusing on a single, complete event.

With films, pogledati film is very common because a film is a single, complete event you watch from beginning to end.

Compare:

Večeras idemo gledati film. – We’re going (somewhere) to watch a film (focus on the activity).
Večeras idemo pogledati film. – We’re going (somewhere) to (completely) watch a film (focus on the whole event as a single unit).

Both are correct; pogledati film is slightly more idiomatic in this context.

Why does the second part say sutra ćemo ići učiti hrvatski instead of just sutra ćemo učiti hrvatski?

Both are grammatically correct, but they’re not identical in meaning:

Sutra ćemo učiti hrvatski.
= Tomorrow we will study/learn Croatian.
Focus is on the activity of studying; it doesn’t say anything about going somewhere.
Sutra ćemo ići učiti hrvatski.
= Tomorrow we will go (somewhere) to study Croatian.
Here you emphasise the act of going to some place (e.g. a course, school, lesson) in order to study.

So ćemo ići učiti combines:

ćemo – future auxiliary (we will),
ići – to go,
učiti – to study / to learn.

The original sentence suggests something like:
Tonight we’re going to (the cinema) to watch a film, and tomorrow we’ll go (to some class/place) to study Croatian.

Why is the conjunction a used instead of i between the two clauses?

Both a and i can translate as and, but they’re used differently:

i = simple and, just adding one thing to another.
a = and / whereas / while / but, typically introduces a contrast or difference between two parts.

In Večeras idemo pogledati film, a sutra ćemo ići učiti hrvatski, a contrasts:

this evening vs. tomorrow
watching a film (free time) vs. studying Croatian (work/learning)

You could say:

Večeras idemo pogledati film i sutra ćemo ići učiti hrvatski.
This is grammatically fine but sounds more like a simple list of two plans, without highlighting the contrast between fun tonight and studying tomorrow.

With a, the sentence feels more like:
Tonight we’re going to watch a film, whereas tomorrow we’ll go study Croatian.

Why is the second part sutra ćemo ići učiti hrvatski in the future tense, but the first part uses the present idemo?

Both clauses refer to future actions, but they use different ways to express future:

Večeras idemo pogledati film. – present with a future meaning
This is very natural in Croatian for plans in the near future when a time word (like večeras) makes the time clear.
Sutra ćemo ići učiti hrvatski. – explicit future (ćemo
- infinitive)
  This is the standard Futur I form in Croatian: auxiliary ću, ćeš, će, ćemo, ćete, će
  - infinitive.

You could also say:

Večeras ćemo ići pogledati film, a sutra ćemo ići učiti hrvatski.
or
Večeras idemo pogledati film, a sutra idemo učiti hrvatski.

The original sentence simply mixes two equally valid future expressions. Stylistically it can give a slight feeling of:

Tonight (definite plan, it’s happening) – present
Tomorrow (a plan in the future) – future tense

Can the word order be changed? For example, can I say Idemo večeras pogledati film or Sutra idemo učiti hrvatski?

Yes. Croatian word order is relatively flexible, and moving adverbs like večeras and sutra usually changes emphasis, not basic meaning.

Examples (all correct):

Večeras idemo pogledati film.
Idemo večeras pogledati film.
Idemo pogledati film večeras.

They all mean essentially the same thing; starting with Večeras emphasises “as for this evening…”.

For the second clause:

Sutra ćemo ići učiti hrvatski.
Sutra idemo učiti hrvatski. (present used for future)
Idemo sutra učiti hrvatski.
Sutra ćemo učiti hrvatski. (without ići)

One important restriction: the clitic ćemo has to stay in the so‑called second position in its clause, so:

Sutra ćemo ići… is correct,
Sutra ići ćemo… is wrong.

Why is it hrvatski and not hrvatski jezik? Does hrvatski by itself mean Croatian language?

Yes. In Croatian, the adjective for a language is often used on its own as a noun:

hrvatski (jezik) – Croatian (language)
engleski (jezik) – English (language)
njemački (jezik) – German (language)

So:

učiti hrvatski – to learn/study Croatian
pričati hrvatski – to speak Croatian

You can say učiti hrvatski jezik, but everyday speech normally just uses hrvatski.

Also note capitalisation:

hrvatski (language, nationality adjective) – lowercase
Hrvatska (the country, Croatia) – uppercase

What case are film and hrvatski in, and why do they look like the basic dictionary forms?

Both film and hrvatski are in the accusative case, because they are direct objects:

pogledati što? – film (what are we going to watch?)
učiti što? – hrvatski (what are we going to study?)

For masculine inanimate nouns like film, the nominative and accusative singular forms are the same:

Nominative: film
Accusative: film

Similarly, the masculine singular adjective hrvatski has the same form in nominative and accusative:

Nominative: hrvatski (jezik) je težak.
Accusative: učiti hrvatski (jezik).

So even though the form doesn’t change, their function in the sentence (object of the verb) tells you they are in the accusative case.

There is no a or the before film or hrvatski. How do you know if it means a film or the film, Croatian or the Croatian language?

Croatian has no articles (no a/an and no the). The ideas of definite and indefinite are expressed by:

context,
word order,
sometimes by using demonstratives (taj film = that film, ovaj film = this film),
or by adding other information (e.g. onaj film o ratu – that film about the war).

In Večeras idemo pogledati film, you would usually translate it as a film, unless the context clearly refers to a specific film already known to both speakers, in which case you could use the film in English.

For učiti hrvatski, in English we normally say learn Croatian or study Croatian, not learn the Croatian, so there is no article anyway. The Croatian sentence itself doesn’t specify definiteness; the context does.

Does učiti mean to learn or to study, and does it ever mean to teach?

učiti in Croatian usually corresponds to both English to learn and to study:

učiti hrvatski – to learn/study Croatian
učiti za ispit – to study for an exam

It can also mean to teach in certain constructions:

učiti nekoga nešto – to teach someone something
e.g. Učim djecu hrvatski. – I teach the children Croatian.

However, for to teach in a more explicit or formal sense, Croatians often prefer other verbs, like:

podučavati – to instruct, to tutor
predavati – to lecture, to teach (as a teacher/lecturer)

In your sentence, učiti hrvatski clearly means to learn/study Croatian, not to teach.

Why is there a comma before a in …, a sutra ćemo ići učiti hrvatski?

In Croatian, a comma is normally used before the conjunction a when it joins two independent clauses (two complete sentences):

Večeras idemo pogledati film,
a sutra ćemo ići učiti hrvatski.

Each part has its own verb and subject (even if the subject we is only explicit in the verb ending), so they are separate clauses, and the comma is required.

This is similar to English:
Tonight we’re going to watch a film, and tomorrow we’ll go study Croatian.

Can I say Večeras ćemo gledati film, a sutra ćemo učiti hrvatski instead? Is there a difference?

Yes, you can, and it’s fully correct:

Večeras ćemo gledati film, a sutra ćemo učiti hrvatski.

Differences in nuance:

gledati vs. pogledati
- gledati film – focus on the activity of watching.
- pogledati film – focus on the film as one complete event you watch.
Presence/absence of ići
- ćemo gledati film / ćemo učiti hrvatski – just saying what you’ll be doing.
- ćemo ići pogledati film / ćemo ići učiti hrvatski – emphasises “we will go (somewhere) in order to do it”.

So:

Večeras ćemo gledati film, a sutra ćemo učiti hrvatski.
= Tonight we’ll watch a film, and tomorrow we’ll study Croatian. (no emphasis on going anywhere)
Večeras idemo pogledati film, a sutra ćemo ići učiti hrvatski.
= Tonight we’re going to go watch a film, and tomorrow we’ll go (somewhere) to study Croatian. (emphasis on going to places for both activities)