Я отвечу попозже, сейчас я занят.

Because отвечу is the future form of the perfective verb ответить.

• я отвечаю = I am answering / I answer
• я отвечу = I will answer / I’ll reply

In this sentence, the speaker means I’ll reply later, so Russian uses the future.

A very important point: отвечу looks similar to a present-tense form, but it is actually future, because it comes from a perfective verb. In Russian, perfective verbs do not have a true present tense; their “present-looking” forms refer to the future.

So:

• отвечать = imperfective, ongoing/repeated action
• ответить = perfective, one completed reply

Here the idea is one future reply, so отвечу fits well.

These are an aspect pair:

• отвечать = imperfective
• ответить = perfective

Russian aspect shows how an action is viewed.

отвечать is used for:

• ongoing action
• repeated action
• general ability or habit

Examples:

• Я отвечаю на письма каждый день. = I answer emails every day.
• Подожди, я отвечаю. = Wait, I’m answering.

ответить is used for:

• one complete reply
• a finished result

Example:

• Я отвечу позже. = I’ll reply later.

In your sentence, the speaker is promising a single future response, so the perfective verb is the natural choice.

попозже means a bit later, somewhat later, or later on.

Compare:

• позже = later
• попозже = a little later / a bit later

So попозже sounds a little softer and more conversational. It often suggests not now, but after some time without being very precise.

Examples:

• Отвечу позже. = I’ll reply later.
• Отвечу попозже. = I’ll reply a bit later.

In everyday speech and texting, попозже is very common and natural.

Yes, it could be omitted.

Russian often drops personal pronouns when the verb form already makes the subject clear. So all of these are possible:

• Я отвечу попозже, сейчас я занят.
• Отвечу попозже, сейчас занят.
• Я отвечу попозже, сейчас занят.

The version with я twice is still natural. It can sound slightly clearer or more explicit, especially in isolation.

Russian does not require the subject pronoun as often as English does, because the verb endings already show the person:

• отвечу already means I will reply

So the repeated я is not grammatically necessary, but it is not wrong.

занят is the short form adjective, and that is what Russian usually uses after an implied to be when describing someone’s current state.

So:

• Я занят. = I am busy.
• Он занят. = He is busy.

The full form занятый is usually used before a noun:

• занятый человек = a busy person

This is a very common pattern in Russian:

• Я готов. = I’m ready.
• Она рада. = She’s glad.
• Он занят. = He’s busy.

So in your sentence, сейчас я занят means right now I’m busy, and the short form is exactly what you expect here.

Yes. It changes for gender and number.

• занят = masculine
• занята = feminine
• занято = neuter
• заняты = plural

So:

• A man would say: Я занят.
• A woman would say: Я занята.
• More than one person would say: Мы заняты.

So your sentence, as written, is said by a male speaker. A female speaker would say:

Я отвечу попозже, сейчас я занята.

Here сейчас means now, right now, or at the moment.

It contrasts with попозже:

• попозже = later
• сейчас = now / at the moment

So the sentence has a clear time contrast:

• I’ll reply later
• right now I’m busy

That contrast is very common in Russian:

• Сейчас не могу, позже сделаю. = I can’t right now, I’ll do it later.

The comma separates two clauses:

• Я отвечу попозже
• сейчас я занят

Each part has its own meaning, and together they form one sentence:

• I’ll reply later, right now I’m busy.

Russian often uses a comma between such clauses even when there is no conjunction like because or and. This is a normal pattern.

You can think of it as an asyndetic connection: the relationship is understood from meaning rather than from a linking word.

Yes. Russian word order is flexible, and changing it changes the emphasis more than the basic meaning.

For example:

• Я отвечу попозже, сейчас я занят.
• Сейчас я занят, отвечу попозже.
• Попозже отвечу, сейчас я занят.

All of these are understandable. The original sentence is natural and neutral.

Very roughly:

• Я отвечу попозже... starts with the promise to reply
• Сейчас я занят... starts with the reason or current situation

So word order in Russian often helps show what the speaker wants to emphasize first.

It is neutral to informal and very natural, especially in everyday conversation or messages.

попозже sounds slightly conversational, which makes the whole sentence feel friendly and normal.

If you wanted to sound more formal or polite, you might say:

• Я отвечу позже, сейчас я занят.
• Извините, я отвечу позже, сейчас занят.
• Отвечу позже, сейчас немного занят.

So the original sentence is perfectly natural for casual everyday use, especially in texting.