Приложение не загрузилось, и мне пришлось перезапустить телефон.

Yes. In modern Russian, приложение is the standard word for a software app/application.

• мобильное приложение = mobile app
• приложение by itself often just means app if the context is clear

A native English speaker might expect something like апп or апликация, but приложение is the normal Russian word.

Because the subject, приложение, is:

• singular
• neuter
• in the past tense

The verb is загрузиться. In the past tense, Russian verbs agree with the subject in gender and number:

• загрузился = masculine
• загрузилась = feminine
• загрузилось = neuter
• загрузились = plural

Since приложение is neuter, you get загрузилось.

Here the reflexive form does not mean the app literally did something to itself. In Russian, many verbs with -ся / -сь have meanings that are just normal dictionary meanings and do not translate as reflexive in English.

Compare:

• загрузить приложение = to load an app
• приложение загрузилось = the app loaded

So загрузиться is the natural intransitive verb for to load in the sense of software starting/opening properly.

The -сь is just a spelling/pronunciation variant of -ся used after vowels:

• загрузилося is not used
• загрузилось is correct

This is a question of aspect.

• загрузилось = perfective
• загружалось = imperfective

In this sentence, не загрузилось means the loading did not successfully happen / complete. That matches English didn’t load very well.

By contrast, не загружалось often suggests:

• it was in the process of loading and wasn’t loading properly, or
• it repeatedly failed to load, depending on context

So:

• Приложение не загрузилось = The app didn’t load.
• Приложение не загружалось = The app wasn’t loading / wouldn’t load.

Both are possible in some contexts, but the perfective не загрузилось is very natural when talking about a failed result.

Мне пришлось means I had to.

But literally, the structure is based on the verb прийтись, which in this kind of sentence is used impersonally and means something like:

• it fell to me
• it turned out that I had to
• I was forced/obliged to

That is why Russian uses the dative case:

• мне пришлось = I had to
• тебе пришлось = you had to
• ему пришлось = he had to

So Russian does not say я пришлось. The structure requires the dative, not the nominative.

Because this is an impersonal construction.

Russian often expresses necessity with impersonal phrases. Instead of saying something exactly like I had to, it says something more like:

• to me, it became necessary
• to me, it fell to do

So the clause has:

• мне in the dative
• пришлось in a fixed impersonal past form
• an infinitive after it

Pattern:

• мне пришлось уйти = I had to leave
• нам пришлось ждать = we had to wait
• ей пришлось позвонить = she had to call

After пришлось, Russian normally uses an infinitive to say what had to be done.

So the pattern is:

• кому? + пришлось + infinitive

Examples:

• мне пришлось уйти = I had to leave
• ему пришлось извиниться = he had to apologize
• нам пришлось перезапустить телефон = we had to restart the phone

So in your sentence:

• мне пришлось = I had to
• перезапустить телефон = restart the phone

Yes, перезапустить means to restart / relaunch.

It is built from:

• за-пустить = to launch/start
• пере-за-пустить = to start again, restart

In tech contexts, перезапустить is common for:

• an app
• a program
• a device
• a process

So:

• перезапустить приложение = restart the app
• перезапустить телефон = restart the phone

A related verb is перезагрузить, which often means reboot / reload. For a phone, both may be understood, though перезагрузить телефон is also very common and may sound even more specifically like reboot the phone.

Because телефон is the direct object of перезапустить, so it is in the accusative case.

For masculine inanimate nouns, the accusative singular is usually the same as the nominative singular:

• телефон (nominative)
• телефон (accusative)

So:

• Я перезапустил телефон. = I restarted the phone.

If it were an animate masculine noun, the accusative would usually match the genitive instead.

Yes, but the meaning would shift slightly.

• мне пришлось перезапустить телефон = I had to restart the phone; circumstances forced this action
• мне надо было перезапустить телефон = I needed to restart the phone / I was supposed to restart the phone

Пришлось often sounds more like:

• there was no real choice
• it became necessary because of the situation

Since the app failed to load, пришлось is a very natural choice.

Yes. И simply means and, linking the two events:

• Приложение не загрузилось, и мне пришлось перезапустить телефон.
• The app didn’t load, and I had to restart the phone.

This is straightforward and natural.

But Russian could also use other connectors depending on style:

• ... поэтому мне пришлось... = ...therefore I had to...
• ... так что мне пришлось... = ...so I had to...
• Поскольку приложение не загрузилось, мне пришлось... = Since the app didn’t load, I had to...

Using и here is simple and idiomatic.

Yes. Russian word order is flexible, though different orders can change emphasis.

Original:

• Приложение не загрузилось, и мне пришлось перезапустить телефон.

Possible alternative:

• Мне пришлось перезапустить телефон, потому что приложение не загрузилось.

Both are correct. The original gives the cause first, then the consequence. That is a very natural order.

You could also move мне for emphasis in some contexts, but the given version is neutral and standard.

Телефон is completely natural in everyday speech. Even if the device is technically a smartphone, Russian speakers often still say телефон.

• перезапустить телефон = restart the phone
• перезагрузить телефон = reboot the phone

If you specifically wanted to emphasize that it is a smartphone, you could say смартфон, but телефон is the most normal everyday choice.

Yes, but that removes the meaning of necessity.

Compare:

• Я перезапустил телефон. = I restarted the phone.
• Мне пришлось перезапустить телефон. = I had to restart the phone.

The second version tells us that restarting the phone was not just an action the speaker chose; it was necessary because the app failed to load.

So пришлось adds an important nuance.

It is neutral and natural. It works well in:

• everyday conversation
• text messages
• tech support situations
• informal writing
• neutral written Russian

Nothing in it sounds unusually formal or slangy. It is a very normal modern Russian sentence.