can someone please tell me why i gain less LP after a long winstreak ?

Because the amount of change in LP upon game completion is based upon your level as a player compared to your match up with opponents and your current League standing.

{quoted}

I carried pretty hard, and i get 11 lp, kinda frustrating :/

LP changes have nothing to do with individual game performance or "scores".

Because your MMR hasn't caught up to where you are playing at and so you have lower MMr for what you're playing against so your LP gains drop.

Umm previous game gave me 21lp ...

never gotten less than 20lp from a win

cuz you just got a 50% win rate and had a negative win rate before.

Idk why this logic is hard for most kids that play this game but its reallly goddamn simple

You dont get rewarded for being a bad player. Lets say you have 30 tests in a year. You get an f on 16 of them. Do you think it matters that you got 2 tests right in a row? you dont magically get an A grade average or bumped up to a d+ just because you won two games. You still failed the other 16. You have a 50% win rate now so the more you win on average the more lp you will get. You are digging yourself out of a hole it shouldnt be an easy magically journey.,

http://euw.op.gg/summoner/userName=MAK87

32 LP / 215W 203L Win Ratio 51%

you need a much steeper win/loss % overall.

if you play long enough at a static rank and dont change much your LP gains and losses drop down to low numbers in either direction to prevent streaks from having an effect (which is statistically bound to happen, you will never reach win a game then guaranteed lose the next one.)

the system has a good grasp when you have such a large volume of games behind you. 7 in a row is not enough to suddenly break that.

i also wont go into your "recently played with" numbers. you can check that out for yourself.

I just thought that playing the same champ could have had an impact.