Po lekcji online zawsze trzeba się wylogowywać z konta.

Because po in the sense of after requires the locative case.

So:

• lekcja = nominative
• po lekcji = locative, meaning after the lesson

This is a very common pattern in Polish:

• po pracy = after work
• po obiedzie = after lunch
• po spotkaniu = after the meeting

So po lekcji online means after the online lesson.

Because online is a borrowed word that is usually indeclinable in Polish. That means it stays the same no matter what case the noun is in.

So even though lekcja changes to lekcji, online stays online:

• lekcja online
• po lekcji online

You could also hear more fully Polish alternatives such as:

• lekcja internetowa
• lekcja zdalna

But lekcja online is very natural in modern Polish.

Trzeba means something like:

• it is necessary
• one has to
• you have to (in a general sense)

So zawsze trzeba się wylogowywać z konta means you always have to log out of the account or one must always log out of the account.

It is an impersonal form, so it does not name a specific person.

Trzeba is more general and impersonal. It often sounds like a rule, instruction, or general necessity.

Musieć is more personal and agrees with a subject:

• Muszę = I must
• Musisz = you must
• Musi = he/she/it must

Compare:

• Po lekcji online trzeba się wylogować.
  = After the online lesson, one has to log out. / You have to log out.

• Po lekcji online musisz się wylogować.
  = After the online lesson, you must log out.

So trzeba is used when the sentence is about a general rule rather than one named person.

Because wylogowywać się / wylogować się is the normal Polish verb for to log out.

Here się is part of the verb pattern. It does not mean oneself in a strong English sense. It is just how this verb is normally used.

Compare:

• zalogować się = to log in
• wylogować się = to log out

So you should learn these as whole verb expressions, not as a plain verb plus a separate optional word.

This is about aspect.

• wylogować się = perfective
• wylogowywać się = imperfective

In this sentence, wylogowywać się fits well because the sentence describes a habitual / repeated rule:

• zawsze = always

So the idea is this is something that must be done regularly, every time.

A sentence with the perfective is also possible:

• Po lekcji online zawsze trzeba się wylogować z konta.

That version focuses more on the action being completed each time. The imperfective wylogowywać się sounds more like an ongoing rule or repeated practice.

It is z konta because the preposition z here means from / out of, and it requires the genitive case.

So:

• konto = nominative
• konta = genitive

That is why Polish says:

• wylogować się z konta = to log out of an account

This is the normal expression.

Yes. Polish word order is more flexible than English word order.

The original sentence is very natural:

• Po lekcji online zawsze trzeba się wylogowywać z konta.

You could also say:

• Zawsze po lekcji online trzeba się wylogowywać z konta.

That also sounds natural.

A useful thing to remember is that się usually stays close to the verb area, and it does not normally go at the very beginning of a sentence.

So trzeba się wylogowywać is more neutral than trzeba wylogowywać się, though both can occur.

Yes. That is the standard and natural expression.

Very commonly you will hear:

• wylogować się z konta
• wylogowywać się z konta

If the context is already clear, Polish can also drop z konta:

• Po lekcji trzeba się wylogować.

That simply means After the lesson, you have to log out.

Because Polish does not have articles like a, an, and the.

English says:

• after the online lesson
• out of the account

Polish just says:

• po lekcji online
• z konta

The meaning of the / a is usually understood from context. That is completely normal in Polish.

Zawsze means always, and here it applies to the whole rule: after the online lesson, logging out is always necessary.

Its position is fairly flexible, but some positions sound more natural than others.

Natural options include:

• Po lekcji online zawsze trzeba się wylogowywać z konta.
• Zawsze po lekcji online trzeba się wylogowywać z konta.

Both mean basically the same thing. The difference is mostly about emphasis:

• sentence-initial zawsze gives stronger emphasis to always
• the original version sounds neutral and natural