U zadnje vrijeme zaboravljam sitnice i ostavljam ključeve na čudnim mjestima.

Because Croatian usually drops subject pronouns when they are already clear from the verb form.

Here, zaboravljam and ostavljam both end in -am, which tells you the subject is ja = I.

So:

• zaboravljam = I forget / I am forgetting
• ostavljam = I leave / I am leaving

You could say Ja u zadnje vrijeme zaboravljam..., but ja is normally omitted unless you want emphasis, contrast, or clarity.

U zadnje vrijeme is a very common expression meaning:

• lately
• recently
• in the last while
• of late

Literally, it is something like in the last time / in recent time, but you should learn it as a fixed phrase.

Why the form?

• vrijeme is a neuter singular noun
• after u in this time expression, Croatian uses the accusative
• so the adjective also matches that form:
  • zadnje vrijeme

You will also hear:

• u posljednje vrijeme

That means the same thing and is often a bit more formal or neutral in style.

Because Croatian present tense often covers meanings that English expresses with:

• I forget
• I am forgetting
• I’ve been forgetting

In this sentence, the present tense describes a current repeated tendency or ongoing habit:

• zaboravljam sitnice = I keep forgetting little things
• ostavljam ključeve... = I keep leaving my keys...

So Croatian does not need a special tense like English present perfect continuous here.

This is about aspect, which is very important in Croatian.

• zaboravljam = imperfective
• ostavljam = imperfective

Imperfective verbs are used for:

• repeated actions
• habits
• ongoing situations
• general tendencies

That fits this sentence perfectly: the speaker is describing something that has been happening repeatedly lately.

Compare:

• zaboravljam sitnice = I keep forgetting little things
• ostavljam ključeve na čudnim mjestima = I keep leaving keys in strange places

The perfective partners are:

• zaboraviti / zaboravim
• ostaviti / ostavim

Those are more about a completed single action, not a repeated pattern.

Sitnice is in the accusative plural because it is the direct object of zaboravljam.

The verb zaboravljati / zaboraviti takes a direct object:

• zaboravljam što? = what am I forgetting?
• sitnice = little things / small details

The base noun is:

• sitnica = a little thing, a small item, a minor detail

Plural:

• sitnice

In this form, nominative plural and accusative plural look the same for this noun, so the form is sitnice.

It can mean both, depending on context.

Sitnica literally refers to a small thing, little matter, minor item, or trifle.

So zaboravljam sitnice could mean:

• I forget little things
• I forget small details
• I forget minor stuff

In this sentence, it suggests everyday forgetfulness: small, unimportant things rather than major facts.

Because ključeve is the accusative plural of ključ.

The noun is:

• ključ = key

Since it is the direct object of ostavljam, it must be in the accusative:

• ostavljam što? = what am I leaving?
• ključeve

So:

• nominative singular: ključ
• accusative singular: ključ
• nominative plural: ključevi
• accusative plural: ključeve

That is why the sentence uses ključeve.

Because here na means at / in / on in the sense of location, not movement toward a place.

Croatian distinguishes:

• na + accusative = motion toward a place
• na + locative = location at a place

In this sentence, the idea is that the keys end up being in strange places, so Croatian treats it as a location:

• na čudnim mjestima = in strange places

That is why mjestima is in the locative plural.

A useful comparison:

• Stavljam ključeve na stol. = I am putting the keys onto the table.
  
  • motion → accusative
• Ključevi su na stolu. = The keys are on the table.
  
  • location → locative

With ostavljati, Croatian often focuses on where something is left, so na čudnim mjestima is natural.

Because adjectives must agree with the noun they describe in:

• gender
• number
• case

The noun is:

• mjesto = place
• plural here: mjestima

After na in this location meaning, mjestima is in the locative plural.

So the adjective must also be locative plural:

• čudnim mjestima = in strange places

The same agreement happens in zadnje vrijeme:

• zadnje matches vrijeme

It is locative plural.

The singular noun is:

• mjesto = place

Plural forms include:

• nominative plural: mjesta
• locative plural: mjestima

Because it comes after na meaning location, Croatian uses the locative:

• na mjestima = in/on places
• na čudnim mjestima = in strange places

Yes. Croatian word order is fairly flexible.

The sentence begins with U zadnje vrijeme because that sets the time frame right away:

• Lately, ...

That is very natural.

You could also say:

• Zaboravljam sitnice i ostavljam ključeve na čudnim mjestima u zadnje vrijeme.

But that sounds less natural, because the time phrase usually fits well at the beginning.

Croatian often puts time expressions early when they provide the background for the whole sentence.

Because Croatian has no articles like English a, an, or the.

So Croatian simply says:

• sitnice
• ključeve
• na čudnim mjestima

Whether English uses the, my, some, or no article at all depends on context and translation.

For example:

• ostavljam ključeve could mean I leave the keys, I leave my keys, or sometimes just I leave keys, depending on context.

In this sentence, English naturally supplies my keys, even though Croatian does not need to say moje ključeve unless it wants extra emphasis or clarity.

Yes:

• U zadnje vrijeme zaboravljam sitnice i ostavljam moje ključeve na čudnim mjestima.

But that sounds less natural in many everyday contexts unless you really want to stress my keys.

Croatian often leaves possession understood when it is obvious from context, especially with personal belongings.

So the original:

• ostavljam ključeve

naturally gets understood as I leave my keys.

Often, yes.

Both are correct and common:

• u zadnje vrijeme
• u posljednje vrijeme

Very roughly:

• u zadnje vrijeme can sound a bit more everyday and conversational
• u posljednje vrijeme can sound a bit more neutral or formal

But in normal speech, both are perfectly natural. A learner should recognize and feel comfortable using either one.

A repeated habit or pattern.

Several things show that:

• u zadnje vrijeme = lately
• zaboravljam = imperfective present
• ostavljam = imperfective present

Together they mean something like:

• Lately I’ve been forgetting little things and leaving my keys in strange places.

So the sentence is not about one single occasion. It describes an ongoing recent tendency.