Wywrotka zdarzyła się blisko brzegu rzeki.

Wywrotka can be ambiguous.

Most commonly, it means a dump truck / tipper truck. But in some contexts it can also mean an overturning, spill, wipeout, or capsize-type accident.

In this sentence, because it happened (zdarzyła się), it is understood as an event, not a vehicle. Without context, though, a learner might pause because the word has more than one meaning.

Because Polish past tense agrees with the subject in gender and number.

Here the subject is wywrotka, which is feminine singular, so the verb is:

• zdarzyła się — feminine singular

Compare the endings:

• -ł for masculine singular
• -ła for feminine singular
• -ło for neuter singular
• -ły / -li for plural

So the -ła tells you the subject is feminine.

Here się is part of the verb zdarzyć się, which means to happen or to occur.

It is not really translated as a separate word in English. In this use, you normally need it. So:

• zdarzyć się = to happen
• without się, you do not get the normal meaning to happen

Its position can move in Polish, but zdarzyła się is the most neutral wording here.

Because blisko normally takes the genitive.

So:

• brzeg → brzegu
• rzeka → rzeki

This gives:

• blisko brzegu = near the bank
• brzeg rzeki = the bank of the river

So rzeki is genitive because Polish expresses of the river with a noun + genitive pattern.

Because after blisko, you cannot keep brzeg in the nominative form.

The base form is:

• brzeg = bank, shore, edge

But after blisko, it must change to the genitive:

• blisko brzegu = near the bank

So brzeg rzeki is the dictionary-style phrase river bank, but inside this sentence it becomes blisko brzegu rzeki.

No, the meaning changes.

• blisko brzegu rzeki = near the river bank
• na brzegu rzeki = on the river bank
• przy brzegu rzeki = by the river bank / right next to it

So blisko means near, not necessarily on the bank itself.

Yes. Polish word order is fairly flexible.

For example, you could also say:

• Blisko brzegu rzeki zdarzyła się wywrotka.
• Zdarzyła się wywrotka blisko brzegu rzeki.

The core meaning stays the same, but the emphasis changes:

• starting with wywrotka highlights the event
• starting with blisko brzegu rzeki sets the scene first

The original sentence sounds normal and neutral.

They are very similar, and both can often be translated as happened.

In many contexts, either one works:

• Wywrotka zdarzyła się blisko brzegu rzeki.
• Wywrotka wydarzyła się blisko brzegu rzeki.

Very roughly:

• zdarzyć się often feels like to happen / occur
• wydarzyć się can sound a little more formal or emphatic

In everyday speech, zdarzyć się is very common.

Because Polish has no articles. There is no direct equivalent of English a / an / the.

So brzeg rzeki can mean either:

• the river bank
• a river bank

Context tells you which one is meant. The same is true for wywrotka.

It is grammatical, but the most natural version depends on what wywrotka is supposed to mean.

If it means something like a boat capsize, a native speaker might prefer a more specific sentence, for example:

• Łódź wywróciła się blisko brzegu rzeki.
• Do wywrotki doszło blisko brzegu rzeki.

The original sentence is understandable, but wywrotka can also mean dump truck, so without context it may sound a little ambiguous.