Ja ne volim uspoređivati sebe s drugima, dok moja prijateljica to radi stalno.

That’s right: Croatian often leaves out subject pronouns because the verb ending already shows the person.

• volim already means I like
• so Ne volim uspoređivati... is a complete sentence by itself

Here, Ja is included for emphasis or contrast. It helps set up the opposition with moja prijateljica later in the sentence:

• Ja ne volim...
• dok moja prijateljica...

So it feels a bit like:

• I don’t like comparing myself with others, whereas my friend does it all the time.

Croatian often uses voljeti + infinitive to mean to like doing something.

So:

• volim čitati = I like reading
• volim putovati = I like travelling
• ne volim uspoređivati = I don’t like comparing

Also note:

• ne is written separately from the verb: ne volim
• this is the normal way to negate most verbs in Croatian

So this part is very natural and common.

This is a question of aspect, which is very important in Croatian.

• uspoređivati = imperfective
• usporediti = perfective

In this sentence, the speaker is talking about a general habit or repeated action, not one single completed comparison. Because of that, Croatian uses the imperfective verb:

• ne volim uspoređivati sebe s drugima = I don’t like comparing myself with others

If you used usporediti, it would sound more like to compare once / to make a completed comparison, which does not fit as well here.

sebe is the reflexive pronoun, used when the object refers back to the subject.

Here, the subject is I, and the person being compared is also I, so Croatian uses the reflexive form:

• uspoređivati sebe = to compare oneself

Why not mene?

• mene means me as a non-reflexive object
• that would suggest someone is comparing me, not that I am comparing myself

Why not just se?

• You very often can say uspoređivati se s drugima
• that is also natural and very common

So:

• uspoređivati se s drugima = to compare oneself with others
• uspoređivati sebe s drugima = a more explicit version, with sebe spelled out

In this sentence, sebe sounds slightly more deliberate or emphatic.

drugima is in the instrumental plural.

The preposition s (or sa) usually takes the instrumental when it means with:

• s prijateljem = with a friend
• s ljudima = with people
• s drugima = with others

So:

• uspoređivati sebe s drugima = to compare oneself with others

This is a good example of a place where Croatian and English structure things differently. English says compare yourself with others or sometimes to others, but Croatian here uses s + instrumental.

Yes. drugima here means others or other people.

It comes from drugi, which usually means other or second, but it can also function like a noun:

• drugi = others
• s drugima = with others

So even though it looks like an adjective historically, in this sentence it works as the equivalent of the English pronoun others.

dok can mean while, but here it is best understood as whereas or while, by contrast.

So the sentence is not mainly about two actions happening at the same time. It is more about a contrast between two people:

• Ja ne volim...
• dok moja prijateljica to radi stalno

So the sense is:

• I don’t like doing this, whereas my friend does it all the time.

In other contexts, dok can also be purely temporal:

• Čitam dok ona kuha = I read while she cooks

But in your sentence, the contrastive meaning is the important one.

to radi literally means does that.

• to = that
• radi = does

Here, to refers back to the whole earlier action:

• uspoređivati sebe s drugima

So instead of repeating the entire phrase, Croatian uses to radi:

• moja prijateljica to radi stalno = my friend does that all the time

This works very much like English do that.

Yes, it could go somewhere else. Croatian word order is fairly flexible.

In this sentence:

• moja prijateljica to radi stalno

the final position gives stalno a natural emphasis, almost like:

• my friend does that all the time

Other possible word orders include:

• moja prijateljica to stalno radi
• moja prijateljica stalno to radi

The first alternative is especially common. The meaning stays basically the same, but the rhythm and emphasis shift a little.

Because it is the subject of the second clause, it is in the nominative singular.

• moja = my
• prijateljica = female friend

Both words are feminine singular nominative, and they agree with each other.

This is the basic dictionary form:

• moja prijateljica = my friend

If it were an object, the form would change, for example:

• Vidim svoju prijateljicu = I see my friend

So this sentence is also a good example of agreement between a possessive adjective and a noun.

Because Croatian has no articles.

English needs words like:

• a friend
• the friend
• the others

Croatian normally does not use separate words for that. The meaning comes from context, word order, or other words like possessives.

So:

• moja prijateljica already clearly means my friend
• drugima means others / other people

A native English speaker often notices this quickly, because English depends heavily on articles, but Croatian does not.

Both are possible, but many speakers would very naturally say:

• Ja se ne volim uspoređivati s drugima or
• Ne volim se uspoređivati s drugima

That version uses the unstressed reflexive se, which is extremely common.

Your sentence:

• Ja ne volim uspoređivati sebe s drugima

is still understandable and grammatical, but it sounds a bit more explicit because it uses sebe.

So for a learner, it is useful to know both patterns:

• uspoređivati se s drugima = very common, everyday phrasing
• uspoređivati sebe s drugima = more explicit, slightly stronger or more deliberate

A few sounds in this sentence may stand out to English speakers:

• đ in uspoređivati is roughly like the j in jam, but softer
• lj in prijateljica is a single sound, similar to the lli in some pronunciations of million
• j in Croatian is pronounced like English y
• c is pronounced like ts

So roughly:

• uspoređivati ≈ u-spo-reh-ji-va-ti
• prijateljica ≈ pri-ya-te-lyi-tsa

The stress can vary by region and speech style, but those consonants are usually the biggest issue for learners.