Spotkajmy się na dworcu o siódmej.

Spotkajmy się is the 1st person plural imperative of spotkać się.

So it means let’s meet or let’s meet up.

A few useful pieces:

• spotkać się = to meet, to meet each other, to meet up
• spotkajmy = let’s meet
• The verb is perfective, so it suggests one completed meeting event.

This is why the whole sentence sounds like a suggestion or proposal: Let’s meet at the station at seven.

Się is part of the verb spotkać się.

In this case, it gives the idea of meeting each other / meeting up. It is not optional here if you mean let’s meet.

Compare:

• spotkać kogoś = to meet someone / run into someone
  
  • Spotkałem Marka. = I met/ran into Marek.
• spotkać się = to meet each other / to meet up
  
  • Spotkaliśmy się w mieście. = We met in town.

So:

• Spotkajmy Marka. = Let’s meet Marek / let’s go see Marek.
• Spotkajmy się. = Let’s meet.

In Polish, dworzec normally goes with na when you mean at the station.

So:

• na dworcu = at the station
• na dworzec = to the station

This is just the normal preposition pattern Polish uses with this noun.

Examples:

• Jestem na dworcu. = I’m at the station.
• Idę na dworzec. = I’m going to the station.

Using w dworcu would usually sound unnatural in standard Polish.

Dworcu is the locative singular form of dworzec.

After na meaning a location, Polish uses the locative:

• dworzec → base form
• na dworcu → at the station

A useful contrast:

• na dworcu = location, so locative
• na dworzec = movement toward, so accusative

When telling the time in Polish, o is followed by an ordinal number in the locative, not a basic cardinal number.

So:

• o siódmej = at seven o’clock
• not o siedem

Why? Because there is an implied noun:

• o siódmej (godzinie) = at the seventh hour

Since godzina is feminine, the number also appears in the feminine form:

• siódma → siódmej after o

More examples:

• o pierwszej = at one
• o drugiej = at two
• o piątej = at five

Yes, but that is completely normal.

The full phrase would be:

• o siódmej godzinie

But in modern Polish, godzinie is usually omitted, so people simply say:

• o siódmej

That is the standard everyday way to say at seven o’clock.

The difference is location versus direction:

• na dworcu = at the station
• na dworzec = to the station

So:

• Spotkajmy się na dworcu. = Let’s meet at the station.
• Jedziemy na dworzec. = We’re going to the station.

This is a very common Polish pattern:

• na + locative = being somewhere
• na + accusative = going to somewhere

Dworzec usually means a station/terminal, often a train station unless context says otherwise.

If Polish speakers want to be more specific, they can say:

• dworzec kolejowy = railway/train station
• dworzec autobusowy = bus station

So na dworcu by itself can mean at the station, with the exact type understood from context.

Yes. Polish word order is fairly flexible.

The most neutral version is:

• Spotkajmy się na dworcu o siódmej.

But these are also possible:

• Spotkajmy się o siódmej na dworcu.
• O siódmej spotkajmy się na dworcu.
• Na dworcu spotkajmy się o siódmej.

The meaning stays basically the same, but the emphasis changes a little.

One important point: się usually does not go at the very beginning of the sentence.

They are different in both form and meaning.

• Spotkajmy się = Let’s meet
  
  • a suggestion, invitation, or proposal
• Spotkamy się = We will meet / We’ll meet
  
  • a statement about the future

Compare:

• Spotkajmy się jutro. = Let’s meet tomorrow.
• Spotkamy się jutro. = We’ll meet tomorrow.

So in your sentence, spotkajmy się is used because the speaker is proposing the meeting.

A rough guide for an English speaker is:

• spot-KAI-mi shyeh

A few details:

• stress is on the second-to-last syllable: spo-TKAJ-my
• aj sounds roughly like eye
• się here sounds close to shyeh
• the ę in się is often not pronounced as a full nasal vowel in normal speech

So a natural approximation is:

• spot-KAI-mi shyeh

Not perfect, but close enough to be understood.