Dopłyniemy do brzegu rzeki przed wieczorem.

Dopłyniemy is the 1st person plural future form of dopłynąć, which means to reach a place by swimming or by boat / by water.

So dopłyniemy means we will reach, we will get there by water, or more literally we will arrive by swimming/sailing/boating.

The exact English translation depends on context:

• if people are swimming: we’ll swim to
• if they are in a boat: we’ll sail/reach
• more generally: we’ll make it to ... by water

Because dopłynąć is a perfective verb.

In Polish, perfective verbs usually form the future with a single form, not with będę / będziemy + infinitive.

So:

• dopłyniemy = we will reach
• not będziemy dopłynąć (incorrect)

A related imperfective verb would be dopływać, and that would describe a repeated or ongoing action, not a completed arrival.

Here the sentence is about successfully reaching the bank, so the perfective verb is the natural choice.

Płynąć means to swim / sail / float / go by water in a general sense.

Dopłynąć adds the idea of reaching the destination.

Compare:

• Płyniemy. = We are sailing / swimming.
• Dopłyniemy do brzegu. = We will reach the shore/bank.

So the prefix do- often gives the sense of getting to the end point.

Because dopłynąć do is the normal pattern for saying to reach something by water.

So:

• dopłynąć do brzegu = to reach the bank / shore
• dopłynąć do wyspy = to reach the island
• dopłynąć do portu = to reach the port

The preposition do usually takes the genitive case, which is why the following nouns change form.

Because after do, Polish normally uses the genitive case.

The basic form is:

• brzeg = bank, shore, edge

After do, it becomes:

• do brzegu = to the bank / shore

So:

• brzeg = nominative
• brzegu = genitive singular

For a similar reason: rzeki is the genitive singular form of rzeka.

Here brzegu rzeki means the bank of the river.

Breakdown:

• rzeka = river
• rzeki = of the river

So:

• brzeg rzeki = the river bank
• literally: bank of the river

In this sentence, the most natural English translation is river bank.

The noun brzeg can mean:

• shore
• bank
• edge

With rzeki (of the river), English normally prefers bank:

• brzeg rzeki = river bank

If it were a sea or lake, shore might sound more natural:

• brzeg morza = seashore / shore of the sea
• brzeg jeziora = lake shore

Yes. By itself, dopłyniemy does not always specify exactly how the movement happens, only that it happens by water.

Depending on context, it could mean:

• we’ll swim there
• we’ll row there
• we’ll sail there
• we’ll reach it by boat

If Polish wants to be more specific, it can add extra words.

Because Polish often omits subject pronouns when the verb ending already shows who is doing the action.

Here -my in dopłyniemy tells you the subject is we.

So:

• dopłyniemy = we will reach

You could say My dopłyniemy..., but that usually adds emphasis, such as:

• We will make it (not someone else).

Without my, the sentence sounds more neutral and natural.

It means before evening.

The preposition przed can mean before in time, and here it is followed by the instrumental case:

• wieczór = evening
• wieczorem = before evening / in the evening, depending on context

In this sentence:

• przed wieczorem = before evening

So the phrase tells us when they will reach the bank.

Because przed requires the instrumental case here.

So:

• wieczór = nominative
• wieczorem = instrumental

That is why the sentence says:

• przed wieczorem = before evening

This is a very common pattern:

• przed obiadem = before lunch
• przed nocą = before nightfall
• przed końcem tygodnia = before the end of the week

The word order is normal and neutral.

Dopłyniemy do brzegu rzeki przed wieczorem. sounds like a straightforward statement:

• We’ll reach the river bank before evening.

But Polish word order is flexible, so other orders are possible for emphasis:

• Przed wieczorem dopłyniemy do brzegu rzeki.
  Emphasizes before evening.
• Do brzegu rzeki dopłyniemy przed wieczorem.
  Emphasizes the destination.

The original version is a good neutral model for learners.

It is understandable, but in natural English river bank is much better.

So the best translation is usually:

• We’ll reach the river bank before evening.

Shore is more common with:

• sea
• ocean
• lake

For a river, bank is the usual word.

A rough English-friendly guide is:

do-pwy-NYE-my

A few pronunciation notes:

• ł sounds like English w
• y is a short Polish vowel with no exact English equivalent
• nie here sounds roughly like nye
• stress in Polish usually falls on the second-to-last syllable, so here the stress is on -nie-: do-pły-NIE-my

So the whole sentence is roughly:

do-pwy-NYE-my do BZHE-gu zhe-KI pshed vye-CHO-rem

That is only an approximation, but it may help at first.