Nie przejmuj się, wszystko będzie dobrze.

In this sentence, przejmuj się means something like worry, get upset, or let it bother you.

The full expression is przejmować się + instrumental / something implied, and it often means:

• to worry about something
• to be bothered by something
• to take something too much to heart

So Nie przejmuj się is a very natural way to say:

• Don’t worry
• Don’t let it get to you
• Try not to be upset about it

It is not a literal word-for-word match with English, but that is the natural meaning.

Się is a very common Polish reflexive particle. In many verbs, it is simply part of the standard verb form and cannot be omitted without changing the meaning or making the sentence unnatural.

Here:

• przejmować = to take over / to take on / to adopt, depending on context
• przejmować się = to worry, to be concerned

So się is essential here because przejmować się is the expression meaning to worry.

Compare:

• Przejmuję się tym. = I’m worried about it.
• Nie przejmuj się. = Don’t worry.

Because this is a command or instruction, not a statement.

Polish uses the imperative for commands:

• przejmuj = worry / be worrying
• nie przejmuj się = don’t worry

By contrast:

• nie przejmujesz się means you are not worrying
• that is a statement, not a command

So:

• Nie przejmujesz się. = You’re not worried.
• Nie przejmuj się. = Don’t worry.

That is the normal way to make a negative command in Polish:

• Zrób to. = Do it.
• Nie rób tego. = Don’t do it.

So:

• Przejmuj się. = Worry / be concerned.
• Nie przejmuj się. = Don’t worry.

This is very straightforward: nie goes before the imperative verb form.

Because dobrze is an adverb, and in this phrase Polish uses the adverb, not the adjective.

• dobry / dobra / dobre = good as an adjective
• dobrze = well / fine as an adverb

In Polish, when you say that a situation will turn out fine, you very often use dobrze:

• Będzie dobrze. = It will be fine.
• Wszystko będzie dobrze. = Everything will be fine.

Even though English uses the adjective fine or good, Polish commonly uses dobrze in this kind of reassuring phrase.

Będzie is the future tense of być (to be), in the third person singular.

Here is the relevant pattern:

• jest = is
• będzie = will be

So:

• Wszystko jest dobrze. = Everything is fine.
• Wszystko będzie dobrze. = Everything will be fine.

It is singular because wszystko is grammatically treated as singular.

In Polish, wszystko means everything, and it takes singular verb agreement.

So you say:

• Wszystko będzie dobrze. not
• Wszystko będą dobrze.

This is similar to English, where everything also takes a singular verb:

• Everything is fine
• Everything will be fine

Even though the meaning is broad and includes many things, grammatically it behaves as singular.

Yes. Nie martw się is also very common and often translates the same way: Don’t worry.

There is a slight difference in feel:

• Nie martw się = don’t worry / don’t be anxious
• Nie przejmuj się = don’t let it bother you / don’t get worked up about it

In many everyday situations, they are interchangeable.

For example:

• Nie martw się, wszystko będzie dobrze.
• Nie przejmuj się, wszystko będzie dobrze.

Both are natural and reassuring.

The comma separates two parts:

1. Nie przejmuj się = a command / reassurance
2. wszystko będzie dobrze = an explanation or follow-up reassurance

It works much like English:

• Don’t worry, everything will be fine.

In Polish, this comma is natural and standard.

Yes, but the original order is the most neutral and natural.

Standard version:

• Nie przejmuj się, wszystko będzie dobrze.

You could also hear:

• Wszystko będzie dobrze, nie przejmuj się.

This changes the emphasis a little:

• first version: the speaker begins with reassurance directed at the person
• second version: the speaker first states the comforting fact, then adds don’t worry

Both are correct, but the original is probably the most common.

It is informal singular, used when speaking to one person you address with ty.

That is because przejmuj is the imperative for ty.

If you want the polite/formal version, you would say:

• Niech się pan nie przejmuje. = to a man
• Niech się pani nie przejmuje. = to a woman
• Niech się państwo nie przejmują. = to more than one person / formal plural

If you want the informal plural form, for more than one person:

• Nie przejmujcie się.

Yes. Very often Polish adds the thing that is causing worry.

For example:

• Nie przejmuj się tym. = Don’t worry about it.
• Nie przejmuj się pracą. = Don’t worry about work.
• Nie przejmuj się egzaminem. = Don’t worry about the exam.

So the short version:

• Nie przejmuj się.

often implies Don’t worry about it / about that from context.

Very natural. It is a common, idiomatic, everyday way to comfort someone.

You could use it when someone is:

• stressed
• upset
• afraid something will go wrong
• embarrassed
• overthinking a problem

It sounds warm and conversational. It is exactly the kind of sentence a native speaker might say in ordinary life.