Завтра я займусь ремонтом.

Because займусь is the perfective future of заняться, while буду заниматься is the imperfective future of заниматься.

In this sentence, займусь suggests:

• I’ll get down to it / I’ll start dealing with it tomorrow
• the action is seen as a whole or as a concrete planned step

By contrast, буду заниматься ремонтом would focus more on the process:

• Tomorrow I’ll be doing repair work
• Tomorrow I’ll spend time working on the repairs

So Завтра я займусь ремонтом often sounds like:

• Tomorrow I’ll get to the repairs
• Tomorrow I’ll take care of the repairs
• Tomorrow I’ll start working on the repairs

It does not necessarily mean the repairs will be finished tomorrow.

The infinitive is заняться.

This verb forms an aspect pair with:

• заниматься — imperfective
• заняться — perfective

So:

• я занимаюсь = I am զբաղված with / I am occupied with / I do
• я займусь = I will get down to / I will take up

In this sentence, the perfective verb fits because the speaker is talking about a specific future action.

The -сь is the reflexive postfix, a variant of -ся.

Russian reflexive verbs often do not translate as literal English reflexives like myself. In many cases, they are just a normal dictionary form of the verb.

Here:

• занять = to occupy, take up
• заняться = to occupy oneself with, to get involved in, to take up

So займусь literally has the reflexive element built into the verb, but in natural English you would usually translate it simply as:

• I’ll deal with
• I’ll work on
• I’ll get to

You do not need to force a translation like I will occupy myself with repairs, although that helps show the structure.

Because заниматься and заняться commonly take the instrumental case.

So:

• заниматься спортом = to do sports
• заниматься музыкой = to study/practice music
• заниматься ремонтом = to do repair work / to work on repairs

That is why the noun appears as:

• nominative: ремонт
• instrumental: ремонтом

This is something you usually learn as part of the verb pattern:

• заниматься / заняться + instrumental

Ремонт usually means repair work, repairs, or sometimes renovation, depending on context.

So ремонтом here could refer to:

• fixing something
• doing household repairs
• doing renovation work

Without more context, the sentence is a bit broad. It could mean:

• Tomorrow I’ll work on the repairs
• Tomorrow I’ll get to the renovation
• Tomorrow I’ll deal with the repair work

Russian often leaves this kind of detail unspecified unless the context makes it clear.

It most naturally means I’ll get to the repairs / I’ll start dealing with the repairs.

The perfective verb заняться usually emphasizes taking something up or turning one’s attention to it, not necessarily completing it.

So the sentence suggests:

• tomorrow is when the speaker will begin dealing with the repairs
• or at least finally devote time to them

If you wanted to say I’ll repair it tomorrow in the sense of completing a repair on a specific object, you might use a different verb, such as отремонтирую.

Compare:

• Завтра я займусь ремонтом. = Tomorrow I’ll get to the repairs.
• Завтра я буду заниматься ремонтом. = Tomorrow I’ll be doing repair work.
• Завтра я отремонтирую это. = Tomorrow I’ll repair/fix it.

Займусь is:

• 1st person singular
• future tense
• from a perfective verb

So it means I will get down to / I’ll take up.

Its basic pattern is:

• я займусь — I will
• ты займёшься — you will
• он / она займётся — he/she will
• мы займёмся — we will
• вы займётесь — you will
• они займутся — they will

Notice that perfective verbs in Russian use simple future forms, not буду + infinitive.

The stress is:

• За́втра
• я займу́сь
• ремо́нтом

A rough pronunciation guide:

• За́втра ≈ ZAV-tra
• займу́сь ≈ zai-MOOSʹ
• ремо́нтом ≈ rye-MON-tam

A few notes:

• In займусь, the final -сь is soft.
• In unstressed syllables, Russian vowels are often reduced, so spelling and pronunciation are not always identical in a fully careful way.

Yes. Russian word order is flexible, and the basic meaning stays the same.

Possible versions include:

• Завтра я займусь ремонтом.
• Я завтра займусь ремонтом.
• Ремонтом я займусь завтра.
• Займусь ремонтом завтра.

The differences are mainly about emphasis and style, not core meaning.

For example:

• Завтра я займусь ремонтом puts tomorrow first, which sounds natural if the time is important.
• Ремонтом я займусь завтра emphasizes the repairs more strongly, perhaps in contrast to something else.
• Я завтра займусь ремонтом is also very natural and neutral.

Normally, no. In this context, ремонт is understood as repair work that needs to be done, not a new long-term activity or career choice.

The verb заняться can sometimes mean take up in a broader sense:

• заняться спортом = take up sports
• заняться бизнесом = go into business

But with ремонтом, especially in an everyday sentence with завтра, the natural interpretation is:

• Tomorrow I’ll work on the repairs
• Tomorrow I’ll deal with the repair work

So it sounds like a practical plan, not a life decision.

Not always. Russian often drops subject pronouns when the verb ending already shows who the subject is.

So you could say:

• Завтра займусь ремонтом.

That still clearly means Tomorrow I’ll get to the repairs, because займусь already tells us the subject is I.

Including я can make the sentence:

• slightly clearer
• slightly more emphatic
• or simply more natural in some contexts

So both are correct:

• Завтра я займусь ремонтом.
• Завтра займусь ремонтом.