Client so slow

It always Get slow when i log in i was good with the legacy client but that make my game slow and when i enter a game and finish it it takes along time in screen boarder but i know because i open close client during game but if i uncheck that my fps go to 30 and when i check it my fps goes to 115 and 120 btw when i enter the champ select it becomes slow i could pick but it becomes too slow it can make me tilted "_" anyone have a Fix please