D i ja učimo hrvatski zajedno.

Probably not. If the meaning shown is You and I are learning Croatian together, the standard sentence should almost certainly be:

Ti i ja učimo hrvatski zajedno.

So D i ja is very likely a typo or a spacing mistake.

• ti = you (singular, informal)
• i = and
• ja = I

I means and.

It is the normal Croatian coordinating conjunction for joining words or phrases:

• ti i ja = you and I
• Ana i Marko = Ana and Marko

It is very common and easy to spot in sentences.

Učimo is the 1st person plural present tense form of učiti = to learn / to study.

It is used because ti i ja = you and I, and that combination takes the same verb form as we.

So:

• ja učim = I learn / I am learning
• ti učiš = you learn / you are learning
• mi učimo = we learn / we are learning
• ti i ja učimo = you and I learn / are learning

Even though you is included, the whole subject is still grammatically we.

It can mean both, depending on context.

Croatian present tense often covers what English expresses with either:

• we learn
• we are learning

So Ti i ja učimo hrvatski zajedno can naturally mean:

• You and I learn Croatian together
• You and I are learning Croatian together

English chooses between simple and progressive more often than Croatian does.

Because učiti focuses on the process of learning, not the completed result.

• učiti = to learn / to study ongoingly
• naučiti = to learn, master, or manage to learn something, often with a sense of completion

In this sentence, the meaning is about the ongoing activity, so učimo is the natural choice.

Very roughly:

• Učimo hrvatski. = We are learning Croatian.
• Naučili smo hrvatski. = We learned / mastered Croatian.

Here hrvatski means the Croatian language.

It comes from the adjective hrvatski = Croatian, but Croatian often uses language names this way without repeating jezik (language).

So both of these can mean the same thing:

• učimo hrvatski
• učimo hrvatski jezik

The shorter version is very common and natural.

It is in the accusative case, because it is the direct object of učimo.

We are learning what?
→ hrvatski

A detail that can confuse learners: in this kind of phrase, the accusative form looks the same as the nominative form, so you do not see a visible ending change here.

So although the form is hrvatski, its function in the sentence is object, not subject.

Because in Croatian, names of languages are normally not capitalized unless they begin a sentence.

So:

• učim hrvatski
• govori engleski
• piše na njemačkom

This is different from English, where Croatian, English, and German are capitalized.

Zajedno means together.

It is an adverb, and it tells us how the action happens:

• učimo zajedno = we learn together
• radimo zajedno = we work together

In this sentence, it emphasizes that both people are learning Croatian with each other.

Yes. Croatian word order is more flexible than English word order.

This sentence can appear in different orders depending on emphasis, for example:

• Ti i ja učimo hrvatski zajedno.
• Ti i ja zajedno učimo hrvatski.
• Hrvatski učimo zajedno.
• Zajedno učimo hrvatski.

These versions are all possible, but they may sound slightly different in focus.

The original order is neutral and natural.

Yes, you could.

Croatian often drops subject pronouns because the verb ending already shows the person and number.

Since učimo already means we learn / we are learning, you can say:

• Učimo hrvatski zajedno.

Adding ti i ja makes the subject explicit:

• Ti i ja učimo hrvatski zajedno.

That can sound clearer, more contrastive, or more personal.

A rough pronunciation guide:

• učimo ≈ OO-chee-mo
• hrvatski ≈ HR-vat-skee
• zajedno ≈ za-YED-no

A few useful notes:

• č sounds like ch in chocolate
• j sounds like y in yes
• hr at the start of hrvatski can feel difficult for English speakers, because Croatian allows consonant clusters that English often does not

You do not need perfect pronunciation immediately, but učimo and zajedno are usually straightforward once you hear them a few times.