Prüfe die Flugnummer, bevor du zum Flugsteig gehst.

Prüfe is the informal singular imperative of prüfen (to check / examine). It is used when telling one person you know well what to do.

• prüfen = infinitive
• du prüfst = you check
• Prüfe! = Check!

So Prüfe die Flugnummer means Check the flight number.

German imperatives change depending on who you are speaking to:

• Prüfe! = to one person informally
• Prüft! = to more than one person informally
• Prüfen Sie! = formal

Die Flugnummer is the direct object of prüfe, because it is the thing being checked.

The noun Flugnummer is feminine, so its basic article is die:

• die Flugnummer = the flight number

In this sentence, the object is in the accusative case, but for feminine nouns, the article stays die in both nominative and accusative:

• nominative: die Flugnummer
• accusative: die Flugnummer

So there is no visible change here.

Bevor means before and introduces a subordinate clause.

That is why the second part is:

• bevor du zum Flugsteig gehst

A subordinate clause in German usually sends the conjugated verb to the end. That is why you get:

• du ... gehst not
• du gehst ...

So the structure is:

• Prüfe die Flugnummer = main clause
• bevor du zum Flugsteig gehst = subordinate clause introduced by bevor

Because bevor creates a subordinate clause. In German subordinate clauses, the finite verb normally goes to the end.

Compare:

• Main clause: Du gehst zum Flugsteig.
• Subordinate clause: ..., bevor du zum Flugsteig gehst.

This is one of the most important German word-order rules to learn.

Common conjunctions that also do this include:

• weil = because
• dass = that
• wenn = if/when
• obwohl = although

German often makes the subject explicit in the subordinate clause, even when the person is obvious from the command.

So:

• Prüfe die Flugnummer, bevor du zum Flugsteig gehst.

literally has you in the second part: before you go to the gate.

That is completely normal. German does not usually omit the subject in a clause like this.

Zum is a contraction of:

• zu dem → zum

Here, zu means something like to, and dem is the dative form of der.

So:

• zum Flugsteig = to the gate / to the boarding gate

This happens often in German:

• am = an dem
• im = in dem
• vom = von dem
• zum = zu dem

The preposition zu takes the dative case.

The noun Flugsteig is masculine:

• nominative: der Flugsteig
• dative: dem Flugsteig

So:

• zu dem Flugsteig → zum Flugsteig

That is why dem is used, not den.

Flugsteig means boarding gate / departure gate at an airport.

In everyday German, many people simply say Gate, especially in airports:

• zum Gate gehen
• den Flugsteig suchen

Both are understandable, but Gate is very common in real-life airport language.

So if you learned the meaning as gate, that is correct.

Yes, you could, and it would be understandable. Both prüfen and kontrollieren can mean to check.

But there can be a small difference in feel:

• prüfen often means check/verify carefully
• kontrollieren can mean inspect/check, sometimes with a sense of making sure something is correct

In an airport instruction, Prüfe die Flugnummer sounds natural and clear.

In German, subordinate clauses are normally separated from the main clause by a comma.

Since bevor du zum Flugsteig gehst is a subordinate clause, the comma is required:

• Prüfe die Flugnummer, bevor du zum Flugsteig gehst.

German uses commas more systematically than English in this kind of sentence.

A natural statement version would be:

• Du prüfst die Flugnummer, bevor du zum Flugsteig gehst.

That means You check the flight number before you go to the gate.

So the only big change is the first verb:

• statement: Du prüfst ...
• command: Prüfe ...

A rough guide for an English speaker:

• Prüfe ≈ PRUE-fuh
• Flugsteig ≈ FLOOK-shtyke

A few details:

• ü is not a normal English oo sound. It is a front rounded vowel. If you know French, it is similar to u in tu.
• eu in bevor sounds like oy.
• ei in Flugsteig sounds like eye.
• st at the start of a syllable in standard German is often pronounced sht, so Steig begins with a sht sound.

Yes, gehst is the present tense form of gehen:

• du gehst = you go / you are going

German often uses the present tense for future meaning when the context makes it clear. In this sentence, it means something like:

• before you go to the gate or
• before you head to the gate

So even though the verb form is present tense, the meaning is naturally future-oriented.