Rekrutacja na to stanowisko skończy się w piątek.

In this sentence, rekrutacja most naturally means the recruitment process for the job.

In English, depending on style, you could translate it as:

• Recruitment for this position will end on Friday.
• The hiring process for this position will end on Friday.
• Applications for this position close on Friday.

That last version is often the most natural in job ads, even though it is not a word-for-word translation.

Because Polish commonly uses na with job positions in expressions like:

• rekrutacja na stanowisko = recruitment for a position
• aplikować na stanowisko = to apply for a position

So na to stanowisko means for this position.

This is just the normal Polish pattern with jobs and posts. It is not a literal translation of English for, but it fills the same role here.

Because stanowisko is a neuter noun.

The Polish demonstrative this changes for gender:

• masculine: ten
• feminine: ta
• neuter: to

So:

• ten urząd
• ta praca
• to stanowisko

That is why you get na to stanowisko.

It actually is in the accusative case, but for this noun the nominative and accusative singular look the same.

So:

• nominative: to stanowisko
• accusative: na to stanowisko

Both forms are spelled the same, which is very common with neuter nouns in Polish.

Skończy się means will end.

The base verb is skończyć się, which means to come to an end / to end / to be over.

So:

• Rekrutacja skończy się w piątek = The recruitment will end on Friday

A useful contrast:

• skończyć coś = to finish something
  
  • Firma skończy rekrutację = The company will finish the recruitment
• skończyć się = to end, to be finished
  
  • Rekrutacja skończy się = The recruitment will end

Się is part of the verb skończyć się.

Without się, the verb usually means that someone finishes something:

• skończyć projekt = to finish a project

With się, it means that something ends by itself as a process or event:

• projekt się skończył = the project ended
• rekrutacja się skończy = the recruitment will end

So in this sentence, się is essential.

Because skończyć się is a perfective verb.

In Polish, perfective verbs do not normally have a true present-tense meaning. Their present-looking forms usually refer to the future.

So:

• kończy się = is ending / ends
• skończy się = will end

This is one of the most important patterns in Polish verbs:

• robi = does / is doing
• zrobi = will do

So skończy się is grammatically the form you use for will end.

Yes, but the meaning shifts a little.

• skończy się w piątek = will end on Friday
  This is clear, complete, and very natural for a deadline or endpoint.
• kończy się w piątek = ends on Friday / is ending on Friday
  This can also be correct, especially in announcements, but it sounds a bit less sharply completed.

You may also hear:

• zakończy się w piątek

This is very close to skończy się w piątek and can sound slightly more formal.

Because Polish commonly uses w with days of the week to mean on a given day:

• w poniedziałek = on Monday
• we wtorek = on Tuesday
• w piątek = on Friday

So w piątek simply means on Friday.

This is a standard time expression, and you should learn it as a set pattern.

It often means on Friday, and the exact interpretation depends on context.

In many real situations, people will understand it as the upcoming Friday.

If you want to be more explicit, you can say:

• w ten piątek = this Friday
• w najbliższy piątek = this coming Friday

So the original sentence is normal, but context tells you which Friday is meant.

Because in Polish, days of the week and months are normally written with lowercase letters.

So:

• poniedziałek
• piątek
• styczeń

This is different from English, where Friday must be capitalized.

Yes. Polish word order is more flexible than English, although some versions sound more neutral than others.

The original sentence:

• Rekrutacja na to stanowisko skończy się w piątek

is a very natural, neutral way to say it.

You could also say:

• W piątek skończy się rekrutacja na to stanowisko

This puts more focus on Friday.

The meaning stays basically the same, but the emphasis changes. Polish often moves elements around to highlight what is most important or most new in the sentence.