Game freezes and I have to restart my whole computer, then repair league

I don't know how this works as this is my first time posting on these forums, but I'm getting really sick of this. All of my stuff is up to date and my hardware is fine. The game will be running fine but then out of no where, it will freeze. I can still move my mouse around but I can't tab out and launch task manager to end the client, so I have to restart my whole computer. Then, I try o launch league and it says that it has to repair. I don't understand how this big of a game is still having these many problems