Если не смогу дозвониться до тебя вечером, напишу в чат.

Russian often drops personal pronouns when the verb ending already makes the subject clear.

• смогу = I will be able
• напишу = I will write

So я is understood automatically. You can say Если я не смогу..., but it usually sounds more emphatic, as if you are contrasting I with someone else.

Смогу means I will be able.

It is the 1st person singular future form used with мочь / смочь. In this sentence, it works like a modal verb:

• не смогу дозвониться = I won’t be able to get through by phone

So the structure is:

• смогу = will be able
• дозвониться = to get through by phone

That is a normal difference between Russian and English.

In Russian, when you talk about a future condition, you can use a future form after если:

• Если не смогу... = If I can’t / If I’m not able to...
• Если будет дождь... = If it rains / If there is rain...

English usually avoids will after if in these cases, but Russian does not have that restriction.

Both are possible, but they are a little different in nuance.

• не смогу дозвониться stresses inability: I won’t be able to get through
• не дозвонюсь is more direct: I won’t get through

The version with смогу sounds a bit more like if I can’t manage to reach you by phone.

This is an important vocabulary point.

• звонить = to call, to be calling
• позвонить = to call once / to make a call
• дозвониться = to successfully get through by phone

So дозвониться does not just mean call. It means the call actually reaches the person, after trying if necessary.

That is why this sentence is not just about making a call. It is about successfully reaching the other person.

It has the reflexive ending -ся, but here it is best learned as part of the whole verb дозвониться.

It does not literally mean something like call oneself. In modern usage, дозвониться до кого-то is simply a fixed verb meaning to get through to someone by phone.

Many Russian -ся verbs are not directly reflexive in the English sense. So the safest approach is to learn дозвониться as one complete verb with its own meaning and pattern.

Because дозвониться uses a different pattern from звонить.

Compare:

• звонить кому-то → dative
  звонить тебе = to call you
• дозвониться до кого-то → до + genitive
  дозвониться до тебя = to get through to you

So after дозвониться, you need до plus the genitive case.

A small detail: тебя is a form that looks the same in both the accusative and genitive, but here it is genitive because до requires genitive.

Russian often uses the instrumental case for parts of the day when meaning in the morning / in the evening / at night.

So:

• утром = in the morning
• днём = during the day
• вечером = in the evening
• ночью = at night

This is a very common time expression pattern, and no preposition is needed.

Because написать в чат is the normal way to say write in the chat / send a message to the chat.

• в чат suggests direction or target: you are sending text into the chat
• в чате would mean in the chat as a location

So:

• написать в чат = to write a message to the chat
• обсуждать что-то в чате = to discuss something in the chat

Both can exist, but after написать, в чат is the usual choice.

Because the sentence begins with a subordinate clause introduced by если:

• Если не смогу дозвониться до тебя вечером = subordinate clause
• напишу в чат = main clause

Russian separates these clauses with a comma, just as English usually does:

• If I can’t reach you in the evening, I’ll write in the chat.

Because this is a real future condition, not a hypothetical or contrary-to-fact one.

Russian uses normal future forms here:

• Если не смогу..., напишу... = If I can’t..., I’ll write...

You use бы for more hypothetical meanings, for example:

• Если бы я не смог дозвониться, я бы написал...
  = If I couldn’t / If I were unable to get through, I would write...

So the original sentence is about a real possible situation in the future.

No, Russian word order is fairly flexible.

The original sentence is natural:

• Если не смогу дозвониться до тебя вечером, напишу в чат.

But you could also hear:

• Если вечером не смогу дозвониться до тебя, напишу в чат.
• Вечером, если не смогу дозвониться до тебя, напишу в чат.

The basic meaning stays the same. The differences are mostly about emphasis and information flow.

In the original version, the condition comes first, and вечером sits naturally inside that condition.

Because написать is a perfective verb, and perfective verbs form the future with a single word.

• напишу = I will write
• буду писать = I will be writing / I will write from the imperfective писать

In this sentence, напишу fits well because it refers to one completed action: sending a message.

So the sentence means something like:

• If I can’t get through, I’ll write a message in the chat.

That is why perfective напишу is the natural choice.