Radim deset ponavljanja.

I do ten repetitions.

Breakdown of Radim deset ponavljanja.

• deset: ten
• raditi: to do
• ponavljanje: an exercise repetition

Questions & Answers about Radim deset ponavljanja.

What does radim mean here?

Radim is the 1st person singular present tense of raditi.

So radim means I do or I am doing, depending on context.

In this sentence, it naturally means something like:

• I’m doing ten repetitions
• or I do ten repetitions

Serbian present tense often covers both the simple present and the present continuous that English separates.

Why is there no word for I in the sentence?

Because Serbian usually doesn’t need a subject pronoun when the verb already shows who is doing the action.

Radim already means I do / I am doing, so ja is unnecessary unless you want emphasis.

• Radim deset ponavljanja. = neutral, normal
• Ja radim deset ponavljanja. = I’m doing ten repetitions (maybe contrasting with someone else)

Can Radim deset ponavljanja mean both I do ten repetitions and I’m doing ten repetitions?

Yes.

That is very common in Serbian. The present tense of an imperfective verb like raditi can express:

• a current action: I’m doing ten repetitions
• a regular habit: I do ten repetitions

Context tells you which meaning is intended.