Jeśli jesteś za, zgadamy się jutro i będziemy w kontakcie.

Jeśli means if.

Yes, you can also say jeżeli. In most everyday contexts, jeśli and jeżeli are interchangeable:

• Jeśli jesteś za...
• Jeżeli jesteś za...

Both mean the same thing. Jeśli is a bit shorter and very common in speech.

Polish usually leaves subject pronouns out when the verb ending already shows who the subject is.

In this sentence:

• jesteś = you are
• zgadamy się = we will agree / we’ll talk it over
• będziemy = we will be

So Polish does not need to say ty or my unless the speaker wants extra emphasis or contrast.

For example:

• Jeśli jesteś za... = If you’re in favor...
• Jeśli ty jesteś za... = If you are in favor...
  This sounds more emphatic.

Być za is a very common expression meaning to be for something, to support something, or to be in favor.

So Jeśli jesteś za means something like:

• If you’re in favor
• If you agree
• If you’re up for it

It is a fixed expression:

• Jestem za. = I’m in favor / I’m in.
• Nie jestem za. = I’m not for it / I’m not in favor.

Good question. Normally, za often introduces what someone supports:

• Jestem za tym pomysłem. = I’m in favor of this idea.
• Jestem za zmianami. = I’m for the changes.

But in conversation, Polish often omits the thing being discussed if it is already clear from context. So:

• Jeśli jesteś za...
  literally feels like If you’re for it...

The object is understood, so it does not need to be said.

Here zgadamy się is best understood as something like:

• we’ll talk tomorrow and sort it out
• we’ll agree on it tomorrow
• we’ll coordinate tomorrow

This is a somewhat colloquial way of speaking. It suggests that the details or final agreement will be settled tomorrow.

Depending on region and speaker, learners may also hear more standard or clearer alternatives such as:

• dogadamy się jutro = we’ll work it out tomorrow
• ustalimy to jutro = we’ll arrange/settle it tomorrow
• skontaktujemy się jutro = we’ll contact each other tomorrow

So the general idea is: we’ll talk tomorrow and come to an arrangement.

This is because Polish perfective verbs use their non-past forms to talk about the future.

So although zgadamy się looks like a present-tense form structurally, it actually means:

• we will agree
• we’ll sort it out

This is very normal in Polish.

Compare:

• robić (imperfective) → robimy = we do / we are doing
• zrobić (perfective) → zrobimy = we will do

Likewise:

• zgadywać się or another imperfective-style form would not be used here for this completed future idea
• zgadamy się expresses a completed future result: tomorrow you’ll reach an arrangement

Się is a very common particle in Polish. In many verbs, it is simply part of the verb’s normal form.

Here, zgadać się / zgadamy się is not just zgadać plus a random extra word. The się belongs to the verb expression.

Very often, verbs with się describe actions involving the subject in a mutual, personal, or idiomatic way. In this case it helps form the meaning to agree with each other / to coordinate / to talk it over.

So it is best to learn zgadać się as a whole unit.

Because w kontakcie is not a verb — it is a phrase meaning in touch / in contact.

So Polish uses the future of być (to be):

• będziemy = we will be
• w kontakcie = in touch / in contact

Together:

• będziemy w kontakcie = we’ll be in touch / we’ll stay in touch

A one-word future form would be possible only with a different verb, for example:

• skontaktujemy się = we will contact each other
• odezwiemy się = we’ll get in touch

But będziemy w kontakcie is a very natural phrase.

Because Jeśli jesteś za is a subordinate clause introduced by jeśli (if), and in Polish subordinate clauses are separated by a comma.

So the structure is:

• Jeśli jesteś za, = If you’re in favor,
• zgadamy się jutro i będziemy w kontakcie. = main clause

This comma is required in standard Polish spelling.

It sounds mostly everyday and fairly natural, but with a small mix of tones:

• Jeśli jesteś za — neutral, conversational
• zgadamy się jutro — rather colloquial
• będziemy w kontakcie — neutral and common, also fine in work/business contexts

So overall, it sounds like something you could say in a casual or semi-professional conversation. If you wanted something a bit more standard or polished, you might say:

• Jeśli jesteś za, ustalimy wszystko jutro i będziemy w kontakcie.

That sounds a little clearer and more standard to many learners.