Nie chodź po trawniku, bo sąsiadka właśnie go podlewa.

Both can translate as don’t go / don’t walk, but they are used a bit differently.

• chodzić is about walking around, moving on foot in a general or repeated way
• iść is more about going in one direction, one specific trip

With po trawniku, Polish very naturally uses chodzić po... for walking on/over/around a surface.

So:

• Nie chodź po trawniku = Don’t walk on the lawn
• Nie idź na trawnik = Don’t go onto the lawn

Both are possible in different situations, but the sentence you have is the most natural one for warning someone not to walk on the grass.

Very simply: nie + the imperative form.

Here:

• chodź = walk / come / go (imperative, singular)
• nie chodź = don’t walk / don’t go

This is the normal way to make negative commands in Polish.

Related forms:

• chodź! = said to one person
• chodźcie! = said to more than one person
• chodźmy! = let’s go / let’s walk

Because po is the preposition commonly used with chodzić when talking about moving on/over/around a surface.

So chodzić po trawniku means something like:

• to walk on the lawn
• to walk over the grass

This does not mean the same as English after here. Polish po has several meanings, and in this sentence it means movement across a surface.

trawniku is the locative singular form of trawnik.

The preposition po requires the locative in this meaning, so:

• trawnik = dictionary form
• po trawniku = on the lawn / over the lawn

This is why the ending changes from -ik to -iku.

Yes, but the meaning would be a little different.

• na trawniku usually describes location: on the lawn
• po trawniku with chodzić emphasizes movement on/over the lawn

Examples:

• Jestem na trawniku. = I’m on the lawn.
• Chodzę po trawniku. = I’m walking on/over the lawn.

So in your sentence, po trawniku is the natural choice because the idea is specifically walking on the grass.

bo means because.

It is very common in everyday speech and is completely normal here.

Compare:

• bo = everyday, conversational because
• ponieważ = also because, a bit more formal or written
• dlatego że = because, often slightly more explicit

So:

• Nie chodź po trawniku, bo sąsiadka właśnie go podlewa. is a very natural spoken sentence.

właśnie here means just now, right now, or at this very moment.

It tells you the watering is happening currently, which is why you should not walk there.

Without właśnie, the sentence would still make sense:

• Nie chodź po trawniku, bo sąsiadka go podlewa.

But właśnie makes it more immediate:

• the neighbor is watering it right now

go means it here, and it refers to trawnik.

So:

• sąsiadka podlewa go = the neighbor is watering it
• go = the lawn

This is a pronoun replacing the noun so that Polish does not have to repeat trawnik.

A useful thing to notice: in Polish, the same form go can mean him or it, depending on context. Here it clearly means it, because it refers to trawnik.

That is the normal position for short unstressed object pronouns in Polish.

So Polish prefers:

• właśnie go podlewa

rather than:

• właśnie podlewa go

The second version is possible in some contexts, but it sounds more marked or stylistically different. The version in your sentence is the standard, natural order.

Because podlewa is imperfective, and it fits an action that is in progress.

• podlewa = is watering
• podleje = will water / will water completely

Since the sentence includes właśnie and describes what is happening right now, Polish uses the imperfective verb:

• sąsiadka właśnie go podlewa = the neighbor is watering it right now

Using podleje here would not fit the idea of an ongoing present action.

Because sąsiadka means female neighbor, while sąsiad means male neighbor.

So the sentence specifically tells you the neighbor is a woman.

• sąsiad = male neighbor
• sąsiadka = female neighbor

In the present tense, both would take a third-person singular verb:

• sąsiad podlewa
• sąsiadka podlewa

So the verb form does not change here, but the noun tells you the gender.

Not completely. Polish word order is more flexible than English, but some orders sound more natural than others.

Your sentence:

• Nie chodź po trawniku, bo sąsiadka właśnie go podlewa.

is very natural.

Other possible versions include:

• Nie chodź po trawniku, bo właśnie sąsiadka go podlewa.
• Nie chodź po trawniku, bo sąsiadka go właśnie podlewa.

These all mean roughly the same thing, but the focus shifts slightly.

The original version sounds smooth and neutral:

• first the warning
• then the reason
• with właśnie naturally highlighting right now

By itself, it is a normal direct command: Don’t walk on the lawn.

Whether it sounds strong or not depends mostly on tone and context. Polish often uses the imperative quite directly, more freely than English sometimes does.

So this can sound:

• neutral and practical, if someone is about to step on wet grass
• stronger, if said sharply
• caring or protective, if said gently

The sentence is not rude by grammar alone. It is just a straightforward warning.