Losing more Lp than gaining but playing against and with higher ranked people

After the new ranking System was implemented i always got about 18 Lp for winning but lost 21 when i lost. I have a winrate about 58% (in my last 20 games i have a 65% winrate) and im always in games with higher ranked (or at least the average mmr is higher than mine) players than me. Also (i know these sites dont show your real mmr) op.gg and lol-mmr shows me that my mmr is higher than the average in my division.

I just dont understand the ranking system tries to keep me in my current rank when i have a positive winrate against !higher! ranked people.

I recently played some duoq with a friend that was unranked and he got placed pretty low, can this affect my mmr or lp gains? It would be nice if someone could help me with my issue and what to do about it.