Kondicija mi je sada bolja.

Here kondicija means physical fitness, stamina, or being in good shape.

In everyday Serbian, kondicija is very often about:

• exercise fitness
• endurance
• overall physical form

So this sentence most naturally means something like My fitness is better now or I’m in better shape now.

Yes, literally mi is the dative singular form of ja and can mean to me.

But in sentences like this, Serbian often uses the dative pronoun to express something that English would usually show with my. So:

• Kondicija mi je sada bolja.
  literally: Fitness to me is now better.
• natural English: My fitness is better now.

This is a very common Serbian pattern. It often sounds more natural than using a possessive adjective.

Yes, absolutely.

• Kondicija mi je sada bolja. = very natural, common
• Moja kondicija je sada bolja. = also correct

The version with moja is a bit more explicit. It can sound slightly more emphatic, as if you are stressing that it is my fitness.

In many everyday contexts, Serbian prefers the dative-pronoun version:

• Ruka mi boli.
• Auto mi je star.
• Kondicija mi je bolja.

Bolja is the feminine singular form of the comparative adjective bolji, which means better.

This comes from dobar (good), but the comparative is irregular:

• dobar = good
• bolji = better

Then it changes to agree with the noun:

• masculine: bolji
• feminine: bolja
• neuter: bolje

Because kondicija is a feminine singular noun, the adjective must also be feminine singular:

• kondicija → bolja

In Serbian, adjectives agree with the noun they describe in:

• gender
• number
• case

Since kondicija is:

• feminine
• singular
• nominative here

the adjective must match it:

• bolja kondicija
• Kondicija je bolja.

If the noun were masculine, you would use bolji:

• Trening mi je bolji.

If it were neuter, you would use bolje:

• Stanje mi je bolje.

Serbian often uses a comparative adjective without stating the second half if it is obvious from context.

So bolja can simply mean:

• better (than before)
• better (than it used to be)
• better (than earlier)

In this sentence, the comparison is understood from sada (now). The idea is:

• Kondicija mi je sada bolja.
• My fitness is better now.

If you want to say it explicitly, you could say:

• Kondicija mi je sada bolja nego pre. = My fitness is better now than before.
• ... bolja nego ranije. = ... better than earlier.

Both mi and je are clitics: short, unstressed words that usually go near the beginning of the sentence.

In this kind of sentence, mi je is the normal and correct order:

• Kondicija mi je sada bolja.

For a learner, the safest rule is:

• learn mi je as a common chunk
• do not switch it to je mi here

You will see this pattern constantly in Serbian:

• To mi je jasno.
• Auto mi je nov.
• Nije mi dobro.

Je is the 3rd person singular present form of biti (to be), in its short/clitic form.

So in this sentence:

• kondicija = fitness
• mi = to me / my
• je = is
• sada = now
• bolja = better

So the structure is basically:

• My fitness is better now.

Yes.

• sada = full form
• sad = shorter everyday form

Both mean now.

So these are both natural:

• Kondicija mi je sada bolja.
• Kondicija mi je sad bolja.

Sad is extremely common in speech.

Yes, Serbian word order is flexible, although some versions sound more neutral than others.

The original sentence is very natural:

• Kondicija mi je sada bolja.

You could also hear:

• Sada mi je kondicija bolja.
• Kondicija mi je bolja sada.

The meaning stays basically the same, but the emphasis changes a little:

• starting with sada emphasizes now
• ending with sada can sound contrastive, like now, as opposed to before

So the given order is a good neutral model to learn first.

Because Serbian does not have articles like English a/an/the.

So Serbian simply says:

• Kondicija mi je sada bolja.

English has to choose:

• My fitness is better now.
• The condition is better now.

Serbian does not mark that distinction with articles.

Mostly, yes. In everyday Serbian, kondicija strongly suggests:

• physical fitness
• stamina
• athletic condition
• being in shape

So this sentence sounds very natural if someone has:

• started exercising
• recovered strength
• improved endurance

If you wanted a broader idea like condition or state, Serbian might use another word such as stanje, depending on context.