Amount of LP given by victories and loses after getting Diamond.

Hey, im playing in eune servers for a couple of years now, this is the second season ive reached diamond. I had about 60% winrate while i was playing in Platinum and i was given about 20-23LP for victories and 13-17 for defeats, but when i got diamond the game started giving me 11LP for victories and 24 for defeats. How exactly can i climb if i have about 70% winrate in diamond but i'm unable to climb? There's no way im even getting diamond 3 if it keeps giving me that amount of LP for victories. Why is this happening?