Learn Turkish: Prova bittiğinde oyuncular çok yorgundu. - When the rehearsal ended, the actors were very tired.

It uses the temporal clause structure you are learning: bit- (to end) + -tik (which softens to -tiğ) + -i (3rd person possessive) + -n- (buffer) + -de (locative "at"). Literally, it means "at the time of its ending."

Why does bittiğinde have a 3rd person possessive ending (-i) if there is no "its" in the sentence?

In Turkish, the subject of a "when" clause is treated as the owner of the action. Here, Prova (the rehearsal) is the subject. So, Prova bittiğinde functionally translates to "at the time of the rehearsal's ending."

Why is there an -n- before the -de in bittiğinde?

Whenever you add a case ending like the locative -de to a 3rd person possessive suffix like the -i here, you must always use the buffer letter -n- to separate them, rather than the usual -y- buffer.

Does bittiğinde inherently mean it happened in the past?