mixing fishes

Question
Can i put sharks ,tiger barbs and fighter fish with mollies?  

Answer
Hi,
No. Sharks are very aggressive fish and will bully all the other fish, Tiger Barbs are also very territorial so will harass the fighter and Mollies, and the Betta (Fighter) will think that the Mollies are other male Bettas, and kill them. So none of the fish will be happy.
Tell me your tank size and if your water is hard or soft, and I'll try to suggest some good fish that will live together.

Best of luck,
Kathryn