Я поповню рахунок і перевірю сигнал на телефоні.

You can often leave it out.

Ukrainian verb forms usually already show the subject:

• поповню = I will top up
• перевірю = I will check

So Поповню рахунок і перевірю сигнал на телефоні is perfectly natural too.

Keeping Я can add:

• a neutral subject at the start of the sentence
• slight emphasis on I
• contrast, as in Я поповню, а ти зачекай = I’ll top it up, and you wait

They are future tense forms.

More specifically, they are the simple future of perfective verbs:

• поповнити → поповню
• перевірити → перевірю

In Ukrainian, perfective verbs often form the future with a single word, where English uses will:

• поповню = I will top up
• перевірю = I will check

Because these verbs are perfective.

Ukrainian has two common future patterns:

• perfective verb → simple future: перевірю
• imperfective verb → compound future with буду: буду перевіряти

So:

• перевірю = I will check once / complete the action
• буду перевіряти = I will be checking / I will check repeatedly or as a process

In this sentence, the speaker means two single completed actions, so the perfective future is the natural choice.

That ending marks first person singular: I.

For many verbs of this type, the I form in the future or present can end in -ю or -у:

• перевірити → перевірю
• поповнити → поповню

So the ending itself helps tell you the subject is I, even without Я.

Here рахунок is the direct object of поповню, so it is in the accusative case.

But for masculine inanimate nouns, the accusative often looks exactly like the nominative:

• nominative: рахунок
• accusative: рахунок

So the form does not change, even though the case function does.

Рахунок has several meanings in Ukrainian, including:

• account
• bill
• score

In this sentence, it means account/balance, especially something you can add money to.

So поповнити рахунок is a very common expression meaning:

• top up an account
• add money to a balance
• recharge credit

Depending on context, it could be a mobile balance, bank account, service balance, and so on.

Yes, it is a very normal and idiomatic phrase.

Literally, поповнити means to replenish / refill / top up, so поповнити рахунок is to top up the account/balance.

A native English speaker may expect something like put money on the phone, and Ukrainian can express that idea in different ways, but поповнити рахунок is one of the most standard ways to say it.

Телефоні is in the locative case, used after the preposition на here.

So:

• телефон = phone
• на телефоні = on the phone

In this sentence, на телефоні means something like:

• on the phone screen
• on the phone itself
• using the phone

It refers to where the signal is being checked.

The pattern is:

• на + locative for location or something situated on something

So на телефоні is not random; it is the regular locative form after на.

Here сигнал most likely means phone signal, reception, or network signal strength.

So the idea is checking whether the phone has service.

In other contexts, сигнал can also mean:

• a signal in the general sense
• a traffic signal
• a beep or alert

But in this sentence, with на телефоні, the intended meaning is almost certainly mobile signal/reception.

Yes. Ukrainian word order is flexible.

The original order is neutral:

• Я поповню рахунок і перевірю сигнал на телефоні.

But you could also say:

• Я перевірю сигнал на телефоні і поповню рахунок.
• Поповню рахунок і перевірю сигнал на телефоні.

Changing the order usually changes the focus or what sounds most important first, not the basic meaning.

Usually yes.

Both і and та can mean and. In many sentences they are interchangeable:

• Я поповню рахунок і перевірю сигнал на телефоні
• Я поповню рахунок та перевірю сигнал на телефоні

That said:

• і is very common and neutral
• та can sound a little more formal or can be chosen for smoother pronunciation

In this sentence, і is the most straightforward everyday choice.

A natural stress pattern is:

Я попо́вню раху́нок і переві́рю сигна́л на телефо́ні.

This matters because Ukrainian spelling usually does not mark stress in normal writing, so learners often need to learn it from dictionaries, teachers, or audio.