bevor, nachdem, während

Three connectors cover almost every relationship between two events. All three are subordinating: the verb goes to the end of their clause.

• Bevor ich zur Arbeit gehe, trinke ich Kaffee.

  Before I go to work, I drink coffee.

  clause first → main clause opens with its verb: trinke ich

• Nachdem ich die Arbeit beendet hatte, bin ich nach Hause gefahren.

  After I had finished work, I drove home.

• Während ich gearbeitet habe, hat mein Freund angerufen.

  While I was working, my friend called.

bevor keeps both clauses in the same tense. Only nachdem steps one tense back — that is the difference you have to hold on to.

Why: bevor already says which event is later, so the tenses do not need to say it again. nachdem puts the earlier event in the clause, and German marks that with the Plusquamperfekt.

• Bevor ich gegessen habe, habe ich die Küche aufgeräumt.

  Before I ate, I tidied the kitchen.

  both Perfekt — no step back

• Nachdem ich aufgeräumt hatte, habe ich gegessen.

  After I had tidied up, I ate.

  same two events, other connector, tense steps back

Those two sentences describe exactly the same evening. Which connector you reach for depends only on which event you put in the clause.

Either clause may come first. Clause first → main clause begins with its verb. Main clause first → the connector follows the comma.

• Ich trinke Kaffee, bevor ich zur Arbeit gehe.

  I drink coffee before I go to work.

  same sentence, other order

• Mein Freund hat angerufen, während ich gearbeitet habe.

  My friend called while I was working.

One warning about während. You met it at A2 as a preposition with the genitive — während der Woche, "during the week". Here it is a conjunction and takes a whole clause. Same word, two jobs, told apart by what follows.