what i must do with my little cat?

Yes, please sterlize / neuter your cat. It will solve the problem. A cat that is neutered will have no desire to look for a female cat. There are many instances of unneutered cats being hit by cars because they lose all their normal sense looking for a mate. if they smell a female, and they normally are cautious of cars they will lose their inhibition. Neutering your cat will keep insure that he has a much longer life with you - both to prevent accidents and to prevent him from having certain cancers later.

get him neutered-- it is the best thing for you and your cat.

It would be a very good idea, for you to have him neutered. That should keep him from running off and looking for girls. It will also help keep the unwanted pet population down. There are so many that are needlessly killed, every day, because of owners letting them run free and multiply. You would be doing a good deed for your kitty, as well as others. You never know what may happen to your kitty out there, away from home. There are many cruel people, and other dangers that could hurt him.

If you neuter your cat, it will solve your problem. He won't have the urge to want to find girl cats. Also, in addition to that - be careful around the house. Close doors tightly so that he cannot push them open and latch them. It will stop the cat from getting out but won't solve your problems because a cat that is intact will do anything to get out to get to a girl cat - rip through screens, and anything you can imagine.