Why is mincraft not working properly ever ?

I have minecraft. I own it. I already Uninstalled the game and reinstalled it. I can no download a texture pack while joining my friends world. The loading menu and download menu are overlapping eachother and all I can do is hit cancel and then it takes me back to my worlds. It won't let me join unless I download the pack but it won't do that. Please help/ fix this game. I have had so many issues with this game in the last two months...

:)