Bonjour Varsha !
These are two different "since" :)
- "Puisque" means "since" in the sense of because, for, as :
Puisque tu ne veux pas m'aider, je vais me débrouiller tout seul.
Since you don't want to help me, I'm going to deal with it myself.
Since you don't want to help me, I'm going to deal with it myself.
- "Depuis" is more of a temporal "since", i.e. from that moment in time :
Je te connais depuis 1994.
I've known you since 1994.
I've known you since 1994.
I hope that's helpful!
Bonne journée !