Jeśli dobrze umyjesz nos i usta zimną wodą, poczujesz się lepiej nawet po długiej podróży.

In Polish, these are future forms of perfective verbs.

• umyć = a perfective verb meaning to wash / wash up completely
• poczuć = a perfective verb meaning to feel / begin to feel

Perfective verbs do not normally have a true present tense for ordinary actions. Their present-looking forms are used to talk about the future.

So:

• umyjesz = you will wash
• poczujesz = you will feel

That is why the sentence means something like:

• If you wash your nose and mouth well with cold water, you will feel better...

This is very common in Polish conditionals.

Because Polish is focusing on a completed action.

• myć = to wash in an ongoing, repeated, or general sense (imperfective)
• umyć = to wash completely / get washed properly (perfective)

Here the speaker means:

• if you wash them properly / once you have washed them properly

So umyjesz fits better than myjesz.

Using myjesz would sound more like a habitual or ongoing action, not a single complete act leading to the result poczujesz się lepiej.

Because in Polish, czuć się means to feel in the sense of to feel a certain way.

Compare:

• czuć coś = to feel/sense something
  • Czuję zimno. = I feel cold.
• czuć się = to feel / to feel oneself / to be feeling
  • Czuję się lepiej. = I feel better.

So:

• poczujesz się lepiej = you will feel better

The się is part of the verb expression here and should be learned together with it.

Because after the verb umyć when you say what you wash something with, Polish uses the instrumental case.

Base form:

• zimna woda = cold water

Instrumental form:

• zimną wodą = with cold water

So:

• umyć nos i usta zimną wodą = to wash the nose and mouth with cold water

This is a very common use of the instrumental case: it often marks the tool, means, or substance used to do something.

Because the preposition po here means after, and after po, Polish usually requires the locative case.

Base form:

• długa podróż = a long journey

Locative after po:

• po długiej podróży = after a long journey

So the pattern is:

• po + locative = after

Examples:

• po pracy = after work
• po obiedzie = after lunch
• po długiej podróży = after a long journey

Because these nouns behave differently in Polish.

• nos = nose and is normally singular here
• usta = literally mouth/lips, but in Polish this word is commonly used in the plural form

So:

• nos i usta = nose and mouth

Even though English says mouth as a singular noun, Polish very often uses usta, which is grammatically plural. This is normal and idiomatic.

Yes, but in this sentence it is best understood as well / properly / thoroughly.

So:

• dobrze umyjesz = wash well, wash properly

It is not about moral goodness or something abstract. It describes how thoroughly the washing is done.

In natural English, you might translate it as:

• if you wash your nose and mouth well
• if you wash your nose and mouth properly

Nawet means even.

Here it adds emphasis:

• poczujesz się lepiej nawet po długiej podróży
• you’ll feel better even after a long journey

The idea is that a long journey usually makes you feel tired or uncomfortable, but this action may help even in that situation.

So nawet strengthens the statement.

Yes, jeśli means if.

In many everyday contexts, Polish can also use:

• jeżeli = a slightly fuller form of if
• gdy = when / if, often a bit more formal or literary depending on context
• jak = sometimes used colloquially in the sense of when/if, but it is not always interchangeable

For a clear learner-friendly sentence like this, jeśli is the most straightforward choice.

Because Polish normally uses a comma to separate the if-clause from the main clause.

So:

• Jeśli dobrze umyjesz nos i usta zimną wodą, poczujesz się lepiej...

This is similar to English when the if-clause comes first:

• If you wash..., you will feel better.

If the order were reversed, Polish punctuation rules can be different depending on structure, but with an opening Jeśli... clause, the comma is standard.

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

The given sentence:

• Jeśli dobrze umyjesz nos i usta zimną wodą, poczujesz się lepiej nawet po długiej podróży.

Possible variations include:

• Poczujesz się lepiej nawet po długiej podróży, jeśli dobrze umyjesz nos i usta zimną wodą.
• Jeśli umyjesz dobrze nos i usta zimną wodą, poczujesz się lepiej nawet po długiej podróży.

The original sounds natural and neutral.
Changing the order may shift emphasis slightly, but the core meaning stays the same.

Yes. That is a very close, structure-by-structure translation.

A few notes:

• Jeśli = if
• dobrze umyjesz = wash well / wash properly
• nos i usta = nose and mouth
• zimną wodą = with cold water
• poczujesz się lepiej = you will feel better
• nawet po długiej podróży = even after a long journey

A more natural English version might vary slightly, but this literal translation matches the Polish grammar quite well.

Both verbs are 2nd person singular: they mean you when speaking to one person.

• umyjesz = you will wash
• poczujesz się = you will feel

So the sentence is addressed to one person.

If you were speaking to more than one person, you would use plural forms:

• umyjecie
• poczujecie się

Example:

• Jeśli dobrze umyjecie nos i usta zimną wodą, poczujecie się lepiej.

Yes. A very common Polish pattern is:

• Jeśli + perfective future, perfective future

So you often get sentences like:

• Jeśli przyjdziesz, porozmawiamy.
  • If you come, we’ll talk.
• Jeśli przeczytasz tę książkę, zrozumiesz temat.
  • If you read this book, you’ll understand the topic.

That is exactly the kind of pattern used here:

• Jeśli dobrze umyjesz..., poczujesz się lepiej.

For English speakers, this can feel unusual at first because the form looks present-like, but in Polish it is normal with perfective verbs.