Zagrevanje i istezanje počinju sada.

They are nouns, not finite verb forms. More specifically, they are verbal nouns: words made from verbs that name an activity or process.

So:

• zagrevanje = warming up / warm-up
• istezanje = stretching

In this sentence, they function as the subject of the verb počinju.

Serbian often uses a singular verbal noun to talk about an activity in general.

So zagrevanje is not necessarily one single warm-up movement. It means the activity of warming up. Likewise, istezanje means the activity of stretching.

That is why the sentence sounds natural even though English might sometimes prefer a plural idea in context.

Those endings are very common in Serbian for forming action nouns from verbs.

For example:

• zagrevati / zagrejati → zagrevanje
• istezati → istezanje

This is similar to how English can turn a verb into something like stretching or heating, except in Serbian these are clearly nouns and behave like regular nouns in grammar.

Because together they make a compound subject: zagrevanje i istezanje = warming up and stretching.

In Serbian, when two subjects are joined by i meaning and, the verb normally agrees with them in the plural.

So:

• Zagrevanje počinje. = The warm-up begins.
• Zagrevanje i istezanje počinju. = Warming up and stretching begin.

That is why počinju is correct, not počinje.

Počinju is present tense, 3rd person plural, from the imperfective verb počinjati.

Here it means something like:

• are beginning now
• are starting now
• begin now

The imperfective verb fits well because it presents the beginning as something happening in the current moment.

It is useful to compare it with the perfective partner:

• imperfective: počinjati → počinju
• perfective: početi → počnu

A learner will often see both verbs, but in this sentence počinju sada is the natural choice for an announcement about something starting right now.

They are in the nominative case because they are the subject of the sentence.

One thing that can confuse learners is that for many neuter nouns, the nominative and accusative singular look the same. So the form itself does not always tell you the case immediately. Here, their job in the sentence tells you they are nominative.

There isn’t one, because Serbian does not have articles like English the and a/an.

So zagrevanje can mean things like:

• warming up
• the warm-up
• a warm-up

The exact meaning depends on context.

If Serbian needs to be more specific, it can use other words such as demonstratives like ovo, to, taj, but there is no separate article system like in English.

Yes. Serbian word order is fairly flexible.

This sentence uses a very natural order:

Zagrevanje i istezanje počinju sada.

But you could also say:

• Sada počinju zagrevanje i istezanje.
• Počinju sada zagrevanje i istezanje.

These versions are grammatically possible, but the emphasis changes a little. Putting sada earlier makes now sound more prominent. The original version is a neutral, straightforward announcement.

The main sounds to watch are:

• č = like ch in church, but usually a bit firmer
• ž = like the sound in measure
• nj = like ny in canyon or Spanish ñ

A rough English-friendly guide would be:

Za-gre-va-nye i is-te-za-nye po-chi-nyu sa-da

More specifically:

• zagrevanje → za-gre-va-nye
• istezanje → is-te-za-nye
• počinju → po-chi-nyu

The spelling is quite regular in Serbian, so once you learn the letter sounds, pronunciation becomes much easier than in English.