U zadnje vrijeme teže zaspim zbog stresa.

U zadnje vrijeme is a very common fixed expression meaning lately or recently.

Here, zadnje is the accusative singular neuter form, and that is the normal form in this expression. Croatian often uses u + accusative in set time phrases.

• u zadnje vrijeme = lately, in recent times
• u zadnjem vremenu sounds more literal, more formal, or more context-specific, and is not the usual everyday way to say lately

So for this meaning, u zadnje vrijeme is the natural choice.

Teže is the comparative adverb of teško.

• teško = with difficulty, hard
• teže = with more difficulty, harder

So teže zaspim means I fall asleep with more difficulty or more naturally in English, I have a harder time falling asleep.

The comparison is understood from context.

Because the sentence starts with u zadnje vrijeme (lately), the listener naturally understands:

• harder than before
• harder than usual

Croatian, like English, often leaves this unstated when it is obvious from context.

Zaspim comes from zaspati (to fall asleep), while zaspavam comes from zaspavati/zaspavati se-type imperfective usage.

In this sentence, zaspim is very natural because the speaker is talking about the whole event/result of falling asleep: each time, it is harder for them to actually fall asleep.

A rough way to think about it:

• zaspim = I do fall asleep, but with difficulty
• zaspavam = I am in the habit/process of falling asleep

In everyday Croatian, teže zaspim is a very common and natural way to express this idea.

This is an important distinction:

• zaspati = to fall asleep
• spavati = to sleep

So this sentence is specifically about the moment of getting to sleep, not about sleep in general.

Compare:

• Teže zaspim. = I have a harder time falling asleep.
• Loše spavam. = I sleep badly.
• Ne spavam dobro. = I do not sleep well.

The preposition zbog always takes the genitive case.

So:

• stres = nominative
• stresa = genitive

That is why you get:

• zbog stresa = because of stress

This is a case pattern worth memorizing:

• zbog + genitive

Because the verb already shows who the subject is.

Zaspim means I fall asleep, since the -im ending marks 1st person singular.

Croatian often leaves out subject pronouns when they are not needed. So:

• teže zaspim = I fall asleep with more difficulty
• ja teže zaspim = I fall asleep with more difficulty

Adding ja is possible, but it gives extra emphasis, like I personally or I, as opposed to someone else.

No. Croatian word order is fairly flexible, and changing it usually changes the focus rather than the basic meaning.

The original sentence is neutral and natural:

• U zadnje vrijeme teže zaspim zbog stresa.

Other possible orders:

• Zbog stresa u zadnje vrijeme teže zaspim.
• Teže zaspim u zadnje vrijeme zbog stresa.

These all mean roughly the same thing, but they highlight different parts of the sentence. The original version sounds very normal in everyday speech.

Both are possible:

• u zadnje vrijeme
• u posljednje vrijeme

Both mean lately / recently.

A few notes:

• u zadnje vrijeme is extremely common in everyday speech
• u posljednje vrijeme can sound a bit more formal or stylistically careful
• some teachers or style guides prefer posljednje, but zadnje is completely normal here

So yes, zadnje is fine.

Yes, but the meaning changes slightly.

• teško zaspim = I have difficulty falling asleep
• teže zaspim = I have more difficulty falling asleep

Because the sentence already says u zadnje vrijeme (lately), the comparative teže fits very well: it suggests that this is worse than it used to be.

So:

• Teško zaspim zbog stresa. = I have trouble falling asleep because of stress.
• U zadnje vrijeme teže zaspim zbog stresa. = Lately, I have a harder time falling asleep because of stress.

Only about falling asleep.

That is because of the verb zaspim from zaspati.

If you want to talk about sleep in general, Croatian would normally use something like:

• Loše spavam. = I sleep badly.
• Ne spavam dobro. = I don't sleep well.
• Imam problema sa spavanjem. = I have problems with sleep / sleeping.

So the original sentence is specifically about difficulty getting to sleep, not necessarily about waking up at night or sleeping badly overall.