Jeśli wszystko pójdzie dobrze, w niedzielę wieczorem będziemy już w nowym mieszkaniu.

Yes, pójdzie is literally will go from the verb pójść (to go, perfective), but in this sentence it is used in the very common expression wszystko pójdzie dobrze = everything will go well.

So Polish often uses go where English uses go too:

• To poszło dobrze. = That went well.
• Mam nadzieję, że wszystko pójdzie dobrze. = I hope everything goes well / will go well.

So this is not strange or idiomatic in a rare way — it is a normal expression.

This is a very common question, because Polish and English behave differently here.

In English, after if, we usually use a present form for future meaning:

• If everything goes well, ...

In Polish, it is normal to use a future form when the meaning is future:

• Jeśli wszystko pójdzie dobrze, ...

So Polish does not follow the same rule as English here. Using the future after jeśli is completely natural.

You can think of it like this:

• English: if + present for future situations
• Polish: jeśli + future is often perfectly normal

Because dobrze is an adverb, and it describes how things go.

• dobry = good (adjective, used with nouns)
• dobrze = well (adverb, used with verbs)

Here the verb is pójdzie (will go), so we need the adverb:

• Wszystko pójdzie dobrze. = Everything will go well.

Compare:

• dobry plan = a good plan
• to działa dobrze = that works well

Because w can mean different things, and the case depends on the function.

1. w niedzielę

Here it means on Sunday — a time expression.

In expressions like days of the week, Polish often uses w + accusative:

• w poniedziałek = on Monday
• w środę = on Wednesday
• w niedzielę = on Sunday

2. w nowym mieszkaniu

Here it means in the new apartment — a location.

For location, w normally takes the locative:

• w domu = in the house
• w pracy = at work
• w mieszkaniu = in the apartment

So:

• w niedzielę = time expression
• w nowym mieszkaniu = physical location

Because wieczorem is the normal Polish adverbial form meaning in the evening / in the evening time.

It comes from the noun wieczór (evening), but here it behaves like a fixed time expression.

Common examples:

• rano = in the morning
• wieczorem = in the evening
• nocą = at night / during the night

So:

• w niedzielę wieczorem = on Sunday evening

This is the natural way to say it.

A form like w wieczór is generally not how Polish says in the evening in normal speech.

Because the sentence is talking about a future state: we will be in the new apartment.

The verb być = to be.
Its future tense is made with forms of będę, będziesz, będzie, będziemy, będziecie, będą.

So:

• jesteśmy = we are
• będziemy = we will be

In this sentence:

• będziemy już w nowym mieszkaniu = we will already be in the new apartment

Since the action/state is in the future, będziemy is necessary.

Już usually means already, but in sentences like this it often has the sense of by then already.

So:

• będziemy już w nowym mieszkaniu
  = we will already be in the new apartment = by that time, we’ll already be in the new apartment

It suggests that by Sunday evening, the move or arrival will have happened.

Compare:

• Będziemy w nowym mieszkaniu. = We’ll be in the new apartment.
• Będziemy już w nowym mieszkaniu. = We’ll already be in the new apartment.

The second one gives a stronger sense of completion by that point.

It is the locative singular, because it comes after w meaning in (location).

The base form is:

• nowe mieszkanie = a new apartment

After w for location, it changes to locative:

• w nowym mieszkaniu = in the new apartment

Both words change:

• nowe → nowym
• mieszkanie → mieszkaniu

This is because adjectives in Polish agree with the noun in gender, number, and case.

Yes, Polish word order is fairly flexible, although some orders sound more natural than others.

The original sentence is very natural:

• Jeśli wszystko pójdzie dobrze, w niedzielę wieczorem będziemy już w nowym mieszkaniu.

Possible variations include:

• Jeśli wszystko pójdzie dobrze, będziemy już w nowym mieszkaniu w niedzielę wieczorem.
• W niedzielę wieczorem, jeśli wszystko pójdzie dobrze, będziemy już w nowym mieszkaniu.
• Jeśli wszystko pójdzie dobrze, już w niedzielę wieczorem będziemy w nowym mieszkaniu.

These shifts can slightly change emphasis:

• placing już earlier can emphasize as early as
• placing w niedzielę wieczorem earlier can emphasize the time

But the original order is neutral and idiomatic.

Because Jeśli wszystko pójdzie dobrze is a subordinate clause introduced by jeśli (if).

In Polish, subordinate clauses are normally separated by a comma:

• Jeśli będziesz miał czas, zadzwoń.
• Gdy wrócę, porozmawiamy.
• Jeśli wszystko pójdzie dobrze, w niedzielę wieczorem będziemy już w nowym mieszkaniu.

So the comma is standard punctuation here.

Not exactly.

jeśli

This means if in a normal, real condition:

• Jeśli wszystko pójdzie dobrze... = If everything goes well...

gdyby

This is more like if in hypothetical or less real situations:

• Gdyby wszystko poszło dobrze... can sound more hypothetical, depending on context.

jak

In some colloquial contexts, jak can mean if, but it is less standard in careful language:

• Jak zdążę, to przyjdę. = If I make it in time, I’ll come.

For a sentence like this, jeśli is the safest and most standard choice.

Pójdzie is perfective.

That matters because in Polish, perfective verbs often express a single completed future event or outcome. Here the meaning is:

• if everything turns out well / goes well

The imperfective partner would be related to iść (to go), but for this expression about outcome, Polish normally uses the perfective form:

• wszystko pójdzie dobrze

Perfective future is especially common when talking about whether something will succeed, happen, or turn out in a certain way.

So this sounds natural because it refers to the result of how things will unfold.

As one natural time unit: on Sunday evening.

It is built from two parts:

• w niedzielę = on Sunday
• wieczorem = in the evening

Together they simply narrow the time down more precisely:

• not just Sunday
• specifically Sunday evening

This is very common Polish structure:

• w sobotę rano = on Saturday morning
• w piątek wieczorem = on Friday evening
• w poniedziałek po południu = on Monday afternoon

So a learner should treat w niedzielę wieczorem as a standard, natural time expression.