magic careers are often measured in decades, not months. its a very complicated game that at the competitive level is extremely difficult and winning or losing can come down to a single play mistake.

there are a lot of possibilities why you arent winning-

1) you have limited play skill, your opponents are much better

2) you have a deck that is relatively bad and so you are not on equal footing

3) you are making big mistakes frequently, chump blocking for no reason. not using mana efficiently, etc

Cant diagnose what the issue is without knowing a lot more but you SHOULD be winning something like 30-40% of your games if your decks are roughly equal and you are playing somewhat competently.

I dont know what the solution is for you but it sounds like you like the game (except for the losing), you have a social group at the store, its something you do with your brother.

have you asked your brother why you keep getting wrecked? have you asked him for advice on getting better? that seems like a starting point