One past occasion: als
A particular event in the past takes temporal als. A whole period can also count as one past setting: the rule is not about how many minutes it lasted.
Als Nora in Wien lebte, arbeitete sie im Theater.
When Nora lived in Vienna, she worked in the theatre.
Repeated occasions: wenn
A repeated past event takes wenn, often with immer. Past tense alone is therefore not enough to choose the connector.
Immer wenn Nora frei hatte, besuchte sie ihre Eltern.
Whenever Nora had time off, she visited her parents.
Present and future situations
Temporal wenn also works for present routines and future events. Depending on context, it can express a condition rather than simply a time. Do not assume every instance means a repeated past event.
Wenn der Zug morgen ankommt, hole ich dich ab.
When the train arrives tomorrow, I will pick you up.
Before versus while
In a sentence with bevor, the main-clause event happens before the event named in the subordinate clause. Temporal während instead describes events whose times overlap.
Ich packe die Tasche, bevor das Taxi kommt.
I pack the bag before the taxi comes.
Keep both clause boundaries in view
The conjugated verb closes the subordinate clause. When that whole clause comes first, the main clause starts with its conjugated verb after the comma.
Während Nora telefoniert, macht Ben Kaffee.
While Nora is on the phone, Ben makes coffee.
Practise this pattern
This explanation is free to read. The matching A2 block includes guided practice, a separate block check and spaced review. The first 10 blocks of each language stay free; other interactive lessons require course access or an eligible seven-day trial.
Explore this grammar blockRelated grammar
References
Original teaching prose and examples, informed by these grammar references. A2 placement is an editorial curriculum choice, not a CEFR certification.