Я взяла талон заранее через приложение, поэтому пришла вовремя.

взяла́ (stress on the last -а́) is the normal pronunciation of the past tense of взять (perfective). It means a completed action: I took / got (it).

брала is past tense of брать (imperfective). You’d use брала if you focus on the process, repetition, or a general habit (e.g., Я часто брала талоны через приложение = I often used to get tickets through the app).
Here, the idea is “I already got one (and it’s done)”, so perfective взяла́ fits best.

In Russian past tense, the verb agrees in gender and number with the subject:

• Я взяла́ = I (female) took/got
• Я взя́л = I (male) took/got
• Мы взя́ли = We took/got

So this sentence implies the speaker is female (or a female grammatical subject).

талон is a very common word in service/administrative contexts. It usually means a queue ticket / appointment slip / number you take to be served (bank, clinic, government office, etc.).
So взять талон often means to get a ticket/number (for your turn), sometimes specifically reserving a time slot.

талон is the direct object of взять, so it’s in the accusative case. For inanimate masculine nouns like талон, the accusative is the same as the nominative:

• талон (Nom.) → талон (Acc.)

So взяла талон = got/took a ticket.

заранее means in advance / ahead of time.

It’s flexible in position, but it typically sits near the verb it modifies:

• Я заранее взяла талон через приложение…
• Я взяла талон заранее через приложение… (your sentence)

Both are natural; the difference is mostly emphasis/rhythm, not meaning.

через has multiple meanings:

1) via / using / through (a method/channel)

• через приложение = via an app / using the app

2) in / after (a period of time)

• через час = in an hour

Here it’s meaning #1: via.

After через (in both “via” and “after” meanings), Russian uses the accusative case.

приложение is neuter, so its accusative looks the same as nominative:

• приложение (Nom.) → приложение (Acc.)

So: через приложение.

In modern Russian, приложение very commonly means a mobile/desktop app (especially with через or в + app name).
It can also mean an attachment (e.g., email attachment or appendix in a document), but in a sentence about getting a талон it’s almost certainly an app.

Because it’s a compound sentence with two clauses:

1) Я взяла талон заранее через приложение
2) поэтому пришла вовремя

The comma separates the clauses, and поэтому introduces the result (“therefore/so”). This punctuation is standard.

All can express result, but they feel slightly different:

• поэтому = therefore / that’s why / so (neutral, common in writing and speech)
• так что = so (often more conversational; literally “so that”)
• из-за этого = because of that (more explicitly “due to that”; can sound slightly more explanatory)

Your sentence with поэтому is a straightforward cause → result structure.

пришла is perfective (one completed arrival): I arrived on time (this time).
приходила is imperfective and usually means repeated/habitual or process: I used to come on time / I was coming on time.

Since this is about one specific situation (got a ticket → arrived on time), пришла is the natural choice.

Yes, word order is flexible:

• … поэтому пришла вовремя. (neutral, very common)
• … поэтому я пришла вовремя. (adds emphasis/clarity on “I”)
• … я поэтому пришла вовремя. (possible, but can sound more colloquial or emphatic; often used to contrast reasons)

The original version is clean and standard.