Learn Hardcore Croatian: Na radionici razgovaramo o tome kako odnos između partnera i sugovornika utječe na učenje jezika. - At the workshop we talk about how the relationship between partners and the person we are talking with affects language learning.

na radionici = at a workshop (as an event / activity)
- similar to na koncertu (at a concert), na sastanku (at a meeting)
u radionici = in a workshop (as a physical space, like a workshop room or garage)
- similar to u kući (in the house), u školi (in the school/building)

So na radionici is correct because it refers to participating in the workshop as an event, not being physically inside a workshop room.

Grammatically:

noun: radionica (workshop)
locative singular: (o) radionici
with preposition: na radionici = at the workshop

What tense is razgovaramo in, and how would I say we will talk or we talked?

Razgovaramo is present tense, 1st person plural of razgovarati (to talk, to have a conversation).

razgovaram – I talk
razgovaraš – you (sg) talk
razgovara – he/she/it talks
razgovaramo – we talk
razgovarate – you (pl) talk
razgovaraju – they talk

In Croatian, the present tense covers both:

English we talk (habitually) and
English we are talking (right now)

To change the time:

we will talk
→ razgovarat ćemo (future I)
(or ćemo razgovarati, same thing, just different word order)
we talked / we were talking
→ razgovarali smo (past tense; assumes a mixed or male group)
→ razgovarale smo (all-female group)

What exactly is o tome doing here? Why not just say razgovaramo kako...?

O tome literally means about that and it introduces the topic you are talking about.

Structure in the sentence:

razgovaramo o tome kako...
= we talk about how...

Details:

o requires locative: o čemu? (about what?)
the pronoun to (that) in locative is o tome

So o tome kako odnos... utječe... can be understood as:

about that – namely, how the relationship ... influences ...
or more naturally in English:
about how the relationship ... influences ...

You normally cannot say razgovaramo kako... on its own to mean we talk about how.... You need o (about) and some object:

razgovaramo o tome kako...
razgovaramo o tome što... (about what...)
razgovaramo o učenju jezika (about language learning)

Why is it kako odnos između partnera i sugovornika utječe... and not da odnos... utječe or što odnos... utječe?

Here kako means how, introducing a clause of manner or way:

kako odnos... utječe na učenje jezika
= how the relationship ... influences language learning

Rough guide:

kako – how, or sometimes that in the sense of the way in which
- Pokazali su nam kako to funkcionira.
  They showed us how it works.
da – neutral that introducing a statement
- Rekla je da dolazi.
  She said that she is coming.
što – what
- Razgovaramo o tome što radimo.
  We’re talking about what we are doing.

In your sentence, the focus is on the way in which the relationship influences learning, so kako (how) is appropriate:

o tome kako... = about how...

You could grammatically say o tome da odnos... utječe..., but that would shift the meaning more toward:

about the fact that the relationship influences...,
not about how it influences...

What case are partnera and sugovornika in, and are they singular or plural?

Both partnera and sugovornika are in the genitive case after između.

The preposition između (between) always takes the genitive:

između koga / čega? – between whom / what?

So:

između partnera i sugovornika
literally: between (the) partner and (the) interlocutor
(or, depending on context, between partners and interlocutors)

Forms:

partner
- genitive singular: partnera
- genitive plural: partnera (same form)
sugovornik
- genitive singular: sugovornika
- genitive plural: sugovornika (same form)

So the form alone doesn’t tell you if it’s singular or plural; that depends on context. In your sentence, it’s natural to understand it as singular nouns used in a general sense, something like:

the relationship between a partner and an interlocutor (in general).

Why does the verb utječe agree with odnos and not with partnera i sugovornika?

The subject of the verb is odnos (relationship), not partnera i sugovornika.

Structure:

kako odnos između partnera i sugovornika utječe na učenje jezika
- odnos = subject (nominative singular masculine)
- između partnera i sugovornika = prepositional phrase modifying odnos
- utječe = 3rd person singular present
- na učenje jezika = prepositional phrase (object of influence)

Croatian, like English, makes the verb agree with the subject, not with nouns inside prepositional phrases.

Compare:

Odnos utječe. – The relationship influences.
Odnos između ljudi utječe. – The relationship between people influences.

In both cases:

subject: odnos (singular)
verb: utječe (3rd person singular)

What does sugovornik mean exactly, and how is it different from govornik?

govornik = speaker
- someone who speaks (e.g. a conference speaker, someone giving a speech)
sugovornik = interlocutor / conversation partner
- the person you are talking with in a conversation

In your sentence:

partner – your partner (e.g. in an exercise, relationship, conversation)
sugovornik – the person you are talking to

So odnos između partnera i sugovornika focuses on the dynamic between you and the person you’re speaking with, not just on someone who is speaking generally.

What is učenje grammatically, and how is it related to the verb učiti?

Učenje is a verbal noun (also called a noun of action) formed from the verb učiti (to learn, to study).

Pattern:

verb: učiti – to learn
verbal noun: učenje – learning

Other examples:

pisati (to write) → pisanje (writing)
čitati (to read) → čitanje (reading)

Grammatically, učenje behaves like a regular neuter noun:

nominative sg: učenje
genitive sg: učenja
etc.

In na učenje jezika:

na
- accusative: na učenje – on/to/for learning
jezika – genitive singular, depending on učenje (see next question)

Why is it učenje jezika and not učenje jezik (or učenje jeziku)?

With verbal nouns like učenje, the “object” of the action usually appears in the genitive case.

Compare:

with the verb:
- učiti jezik – to learn a language (direct object: jezik, accusative)
with the noun:
- učenje jezika – learning of a language (complement: jezika, genitive)

This is very common in Croatian:

čitanje knjige – reading (of) a book
pisanje eseja – writing (of) an essay
učenje jezika – learning (of) a language

So:

jezika is genitive singular of jezik, dependent on the noun učenje.
učenje jezik or učenje jeziku would be ungrammatical here.

Can I move parts of the sentence around, for example say Razgovaramo na radionici o tome... or Razgovaramo o tome na radionici...?

Yes. Croatian word order is relatively flexible, and these variants are grammatical, with only slight differences in emphasis.

All of these are acceptable:

Na radionici razgovaramo o tome kako odnos... utječe na učenje jezika.
– neutral; mild emphasis on at the workshop as the setting.
Razgovaramo na radionici o tome kako odnos... utječe na učenje jezika.
– slightly more focus on the activity we talk (at the workshop) about....
Razgovaramo o tome na radionici kako odnos... utječe na učenje jezika.
– still possible; now o tome (about that) gets a bit more focus as the topic, and na radionici is additional information about where.

Key points:

You usually want razgovaramo o tome to stay together, because razgovarati o (čemu) is a standard pattern.
Na radionici can move more freely as a time/place expression:
- Na radionici, danas, ovdje, etc. often go at the beginning or just after the verb.