I HAVE A PROBLEM PLEASE HELP

I've been issues where I go into a game and all a sudden during the game I get disconnected and it says trying to reconnect but the thing is I can't reconnect even tho my internet is fine. when I alt-tab all the sudden I hear I reconnected but when I click back in it goes back to reconnecting. And when i tried to fix it i had to delete the game and reinstall the game so its not me whos the problem but league and when i play other games i do fine.