Kada putujem, uvek stavljam pasoš u torbu.

In Serbian, the subject pronoun is often omitted when it is clear from the verb ending.

Here, both putujem and stavljam are 1st person singular present tense, so they already mean I travel and I put / I place.

So:

• Kada putujem = When I travel
• uvek stavljam = I always put

You could add ja for emphasis:

• Kada ja putujem, uvek stavljam pasoš u torbu.

But normally it is unnecessary.

Yes. Kada means when, and it can be used both:

1. in a question

   • Kada putuješ? = When are you traveling?

2. in a subordinate clause

   • Kada putujem, uvek stavljam pasoš u torbu. = When I travel, I always put my passport in the bag.

So in your sentence, kada introduces the time clause when I travel.

Putujem is the 1st person singular present tense of putovati, which means to travel.

A few forms:

• ja putujem = I travel
• ti putuješ = you travel
• on/ona/ono putuje = he/she/it travels
• mi putujemo = we travel
• vi putujete = you travel
• oni/one/ona putuju = they travel

In this sentence, the present tense has a habitual/general meaning:

• Kada putujem... = Whenever I travel... / When I travel...

Uvek means always.

In this sentence:

• Kada putujem, uvek stavljam pasoš u torbu.

it modifies stavljam and shows that this is a regular habit.

Its position is flexible, but this placement is very natural. You may also hear:

• Uvek stavljam pasoš u torbu kada putujem.
• Kada putujem, pasoš uvek stavljam u torbu.

The original version sounds neutral and natural.

Stavljam is the 1st person singular present tense of stavljati, meaning to put, to place, or to put into.

In this sentence:

• stavljam pasoš u torbu = I put the passport into the bag

Because stavljati is imperfective, it often describes a repeated or habitual action. That matches the idea of always:

• uvek stavljam = I always put

If you wanted a one-time completed action, Serbian often uses the perfective partner staviti in appropriate contexts.

Pasoš means passport.

Here it is in the accusative singular, because it is the direct object of stavljam.

For masculine nouns like pasoš that refer to inanimate things, the accusative singular is usually the same as the nominative singular.

So:

• pasoš = nominative singular
• pasoš = accusative singular

That is why the form does not change here.

This is a very important Serbian pattern.

With u:

• u + accusative usually means movement into something
• u + locative usually means location in something

So:

• stavljam pasoš u torbu = I put the passport into the bag
  (torbu = accusative)

But:

• pasoš je u torbi = the passport is in the bag
  (torbi = locative)

So the sentence uses u torbu because the action involves putting something into the bag.

Torba is a feminine noun. In the accusative singular, many feminine nouns ending in -a change that ending to -u.

So:

• torba = nominative singular
• torbu = accusative singular

Since u torbu shows motion into the bag, the noun must be in the accusative.

Similar examples:

• knjiga → knjigu
• soba → sobu
• kutija → kutiju

It talks about a habit or a general repeated action, not necessarily something happening at this exact moment.

That is because of the combination:

• Kada putujem = When I travel / Whenever I travel
• uvek = always
• stavljam = present tense, often used for repeated actions

So the whole sentence means something like:

• Whenever I travel, I always put my passport in my bag.

This is a very common use of the Serbian present tense.

Yes, Serbian word order is more flexible than English word order, though some versions sound more natural than others.

Original:

• Kada putujem, uvek stavljam pasoš u torbu.

Other possible versions:

• Uvek stavljam pasoš u torbu kada putujem.
• Pasoš uvek stavljam u torbu kada putujem.
• Kada putujem, pasoš uvek stavljam u torbu.

The original sentence is neutral and natural. Changing the order can shift emphasis:

• putting uvek earlier emphasizes always
• putting pasoš earlier emphasizes passport

Yes. Kad is a very common shorter form of kada.

So you could also say:

• Kad putujem, uvek stavljam pasoš u torbu.

Both are correct. In many everyday situations, kad sounds more conversational, while kada can sound a little fuller or slightly more formal, though both are very common.

Yes, if you want to specify my bag.

• Kada putujem, uvek stavljam pasoš u moju torbu.

But Serbian often leaves out possessives like my when they are obvious from context, especially with personal belongings.

So:

• u torbu often naturally implies into my/the bag, depending on context

If you want to be more idiomatic, you might also hear:

• u svoju torbu = into my own bag

That can sound more natural than u moju torbu in some contexts, especially when referring back to the subject.