Kašljem zbog prehlade.

In Serbian, the verb ending already tells you the subject, so kašljem by itself means I cough or I am coughing.

• kašljem = I cough / I’m coughing
• kašlješ = you cough
• kašlje = he/she coughs

Because of that, ja is usually omitted unless you want emphasis or contrast:

• Ja kašljem, a on kija. = I’m coughing, and he’s sneezing.

So in your sentence, Kašljem zbog prehlade. is completely natural.

Kašljem comes from the verb kašljati, which means to cough.

Here is a useful mini-pattern:

• kašljati = infinitive
• kašljem = I cough
• kašlješ = you cough
• kašlje = he/she coughs

So kašljem is the 1st person singular present tense form.

It can mean both.

In Serbian, the present tense often covers both the simple present and the present continuous from English, depending on context.

So:

• Kašljem. can mean I cough or I’m coughing
• Kašljem zbog prehlade. usually feels like I’m coughing because I have a cold / I cough because of a cold

English makes a stronger distinction than Serbian does here.

Zbog means because of, due to, or on account of.

It is a preposition, and an important thing to remember is that zbog is followed by the genitive case.

Examples:

• zbog kiše = because of the rain
• zbog bolesti = because of illness
• zbog prehlade = because of a cold

So in your sentence:

• Kašljem zbog prehlade.
• literally: I cough because of a cold.

Because zbog requires the genitive case, and prehlade is the genitive singular form of prehlada.

The noun is:

• prehlada = a cold

Its forms include:

• prehlada = nominative singular
• prehlade = genitive singular

So:

• Imam prehladu. = I have a cold.
  Here prehladu is accusative.
• Kašljem zbog prehlade. = I’m coughing because of a cold.
  Here prehlade is genitive after zbog.

Prehlada is a feminine noun.

A good clue is that it ends in -a, which is very common for feminine nouns in Serbian.

Because it is feminine, its case endings follow common feminine patterns, such as:

• prehlada = nominative
• prehlade = genitive
• prehladu = accusative

That is why you see prehlade after zbog.

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

The neutral order here is:

• Kašljem zbog prehlade.

But you could also say:

• Zbog prehlade kašljem.

That version puts more emphasis on because of the cold.

Both are correct. The difference is mostly about focus and style, not basic meaning.

Yes, but the structure changes.

• zbog + genitive noun = because of + noun
• jer + clause = because + full sentence

So:

• Kašljem zbog prehlade. = I’m coughing because of a cold.
• Kašljem jer sam prehlađen / prehlađena. = I’m coughing because I have a cold / because I’m sick with a cold.

Use zbog when you want a noun phrase. Use jer when you want a whole clause.

The trickiest part is usually lj.

• lj is pronounced like the lli in some pronunciations of million, or like the gl sound in the Italian famiglia
• It is treated as a single Serbian letter

So kašljem is roughly:

• KASH-lyem

Very roughly:

• kaš sounds like kash
• ljem sounds something like lyem

Also:

• š is pronounced like sh in shoe

So:

• kaš = kash
• kašljem ≈ KASH-lyem

Yes, it is natural and correct.

A native speaker could definitely say:

• Kašljem zbog prehlade.

Depending on the situation, they might also say:

• Imam prehladu i kašljem. = I have a cold and I’m coughing.
• Kašljem jer sam prehlađen / prehlađena. = I’m coughing because I have a cold.

But your original sentence is perfectly normal and idiomatic.