Was my refusal to postpone the discussion about his repentance from taking bribes a mistake, and did it deprive him of the opportunity for guidance and change after marriage?

Bribery is forbidden and a major sin. The Prophet, peace and blessings be upon him, cursed the one who gives and the one who takes a bribe. Therefore, the one who commits bribery is a transgressor and does not deserve to marry a believing woman, because he is not her equal, and he is not pleasing in his religion and character. Thus, refusing to associate with a young man who takes bribes and refuses to discuss the matter before marriage is a sound decision.