1) А где же часы?
what's the meaning of Же in this sentence?
усилительная частица - indeed, after all
Sample:
кто же это был? — who was it, indeed [after all]?
2) Во повезло, да?
I know that Повезло means lucky but why they put Во before it? does it mean anything?
Во ~ Вот , more informal ,like here!
3) Да мне нельзя
what does it mean?
мне нельзя - this word have main sense
Something doesn't agree with me.
"Да" for emotional intensification ( употребляется для эмоционального усиления, подчеркивания - but, oh but; why; well )
да ты готов! — oh, but you are ready!
да не может быть! — but it can't be true!