Learn Hardcore Russian: Если приложение работает медленно, попробуй перезапустить устройство. - If the app is working slowly, try restarting the device.

In this sentence: Если приложение работает медленно... = If the app is working slowly...
Если introduces a condition on which something else depends.

Important: если is not used for if/whether in indirect questions. For that, Russian uses ли:

Я не знаю, будет ли дождь. – I don’t know if / whether it will rain.
(Using если here would be wrong.)

So: use если for conditional if, and ли for if/whether in reported yes/no questions.

Why is работает (present tense) used, not будет работать (future)?

Russian often uses the present tense in если-clauses even when English uses a future.

Если приложение работает медленно, попробуй...
Literally: If the app works slowly, try...
Natural English: If the app is running slowly / If the app runs slowly, try...

This can describe:

A general rule/habit: Whenever it works slowly, do this.
A realistically possible situation, including in the near future.

You can also say:

Если приложение будет работать медленно, попробуй перезапустить устройство.

That version sounds a bit more like a specific future situation (e.g. If it happens to run slowly later...). Both are grammatically correct; the original is a neutral instruction-style rule.

Why is there a comma after медленно?

The comma separates a subordinate clause from the main clause.

Если приложение работает медленно, – subordinate clause (condition)
попробуй перезапустить устройство. – main clause (result / instruction)

In Russian, you must put a comma between an если-clause and the main clause:

Если ... , ...
or ..., если ...

Leaving the comma out here would be considered incorrect punctuation.

Which case is приложение in, and why?

Приложение is in the nominative singular.

It is the subject of the verb работает.
Pattern: что делает? – приложение работает (what is doing something? – the app is working).

Приложение is a neuter noun ending in -ие; its nominative singular form is приложение, which is exactly what you see in the sentence.

What form is попробуй, and why is it used instead of попробовать?

Попробуй is the imperative, 2nd person singular of попробовать (to try).

попробовать – infinitive (to try)
попробуй – try! (to one person, informal)
попробуйте – try! (to several people or polite/formal)

In the sentence:

попробуй перезапустить устройство = try to restart the device.

We use the imperative to give advice or instructions. Using the infinitive попробовать alone here (… попробовать перезапустить устройство) would be ungrammatical; you need a finite verb form, and the imperative is the natural choice.

Could we use попытайся or постарайся instead of попробуй? What is the nuance?

Yes, grammatically you can say:

Попытайся перезапустить устройство.
Постарайся перезапустить устройство.

Nuances:

попробуй – neutral, the most common: try, give it a try.
попытайся (from пытаться/попытаться) – make an attempt, see if you can. Slightly more about the attempt, sometimes sounds a bit more “serious”.
постарайся (from стараться/постараться) – make an effort, do your best. Emphasizes effort rather than just giving it a go.

In tech instructions, попробуй(те) is by far the most natural: short and neutral.

Why is перезапустить in the infinitive, not the imperative перезапусти?

Because it depends on попробуй in the construction попробуй + infinitive.

попробуй перезапустить устройство
literally: try to restart the device.

The pattern is:

попробуй + [infinitive] = try to [do something]
e.g. попробуй открыть файл – try to open the file.

If you want to give a simple direct command without try, you’d use the imperative of перезапустить:

Перезапусти устройство. – Restart the device.

But you normally do not stack two imperatives (попробуй перезапусти устройство sounds unnatural). Instead: попробуй перезапустить устройство.

Why is the perfective verb перезапустить used, not the imperfective перезапускать?

Перезапустить is perfective; перезапускать is imperfective.

With попробуй, Russian almost always uses a perfective infinitive when you mean try to perform one complete action:

попробуй перезапустить – try to restart (once, fully)

The imperfective перезапускать would sound odd here; it suggests an ongoing or repeated process:

попробуй перезапускать устройство – more like try (as a general practice) repeatedly restarting the device, which doesn’t fit the context.

So: попробуй + perfective infinitive is the standard pattern for “try to do (once / as a single action)”.

What is the difference between перезапустить устройство and перезагрузить устройство?

Both can be used about restarting a device, but there are nuances:

перезагрузить устройство – very common tech phrase meaning to reboot, to restart (by shutting down and starting the system again). This is often the default instruction for phones/computers.
перезапустить устройство – literally to start (launch) it again.
More commonly used with software: перезапустить приложение/программу/службу (restart the app/program/service), but it can also be used for devices, especially in informal speech or certain tech contexts.

So many native speakers would actually expect:

Если приложение работает медленно, попробуй перезагрузить устройство.

The sentence with перезапустить устройство is still understandable and acceptable; it just sounds slightly less standard than перезагрузить in this exact context.

Which case is устройство in, and why doesn’t its form change?

Устройство is in the accusative singular as the direct object of перезапустить:

(что?) перезапустить устройство – to restart what? – the device.

Because устройство is a neuter inanimate noun in -о, its nominative and accusative singular look the same:

Nominative: устройство – the device (is here)
Accusative: устройство – restart the device

So the form doesn’t change, but the syntactic role is different.

How would the sentence change if I spoke formally or to several people?

You change only the imperative verb:

Informal singular (to one person you say ты to):
Если приложение работает медленно, попробуй перезапустить устройство.
Formal / plural (to вы):
Если приложение работает медленно, попробуйте перезапустить устройство.

Everything else stays the same. Пробуйте would sound like “(you) be trying,” so the correct polite imperative is попробуйте.

Can I say Если приложение медленно работает... instead of Если приложение работает медленно...?

Yes, both word orders are grammatically correct:

Если приложение работает медленно...
Если приложение медленно работает...

Word order in Russian is fairly flexible. The difference is mainly in emphasis:

работает медленно – more neutral, slightly emphasizes the result (the way it works: slowly).
медленно работает – can put a bit more focus on the slowness itself, but in everyday speech they’re almost interchangeable.

In instructions like this, the original работает медленно sounds very natural.

Why is there no possessive pronoun like своё or твоё before устройство?

Russian often omits possessive pronouns (my, your, his, etc.) when the owner is obvious from context.

Here, you’re clearly talking to the user about their device, so устройство alone is enough.

Possible variants:

попробуй перезапустить устройство – neutral, default.
попробуй перезапустить своё устройство – your own device; adds a slight emphasis on it being your device (e.g. not someone else’s).

Твоё устройство is grammatically fine, but in this kind of technical instruction устройство or своё устройство would be more typical than твоё устройство.

Could we replace если with когда here? How would the meaning change?

You can say:

Когда приложение работает медленно, попробуй перезапустить устройство.

but there’s a nuance:

если – if: a condition, something that may or may not happen.
когда – when: a time reference; it suggests this situation does happen (or will definitely happen).

So:

Если приложение работает медленно... – If the app (happens to) run slowly... (maybe it does, maybe it doesn’t).
Когда приложение работает медленно... – When the app runs slowly... (implies it does run slowly at times and you’re describing what to do then).

In troubleshooting/instruction texts, если is more typical because it frames the problem as a possible condition.

Sometimes I see если ..., то .... Why is there no то in this sentence?

In Russian conditional sentences, то is an optional particle that corresponds roughly to English then:

Если приложение работает медленно, то попробуй перезапустить устройство.

vs.

Если приложение работает медленно, попробуй перезапустить устройство.

Both are correct. Adding то:

can make the structure a bit clearer or more formal,
slightly emphasizes the consequence part.

In everyday instructions, it’s very common (and perfectly correct) to drop то, as in the original sentence.

Where is the stress in the main words of this sentence?

Stressed syllables are marked with an accent:

Е́сли – Е́с-ли
приложе́ние – при-ло-же́-ни-е
рабо́тает – ра-бо́-та-ет
попро́буй – по-про́-буй
перезапусти́ть (infinitive) – пе-ре-за-пус-ти́-ть
устро́йство – ус-тро́й-ство
ме́дленно – ме́-длен-но

The forms in the sentence are:

Е́сли приложение рабо́тает ме́дленно, попро́буй перезапусти́ть устро́йство.