Riot matchMaking Logic

let's jump right to the point
so recently ..i was getting +20 / +18 LP..in my games ...i thought that my mmr is LOW...but after checking OP.GG i find-out that my mmr is higher then my current Rank(i know that OP.GG don't use the same alogarithm as riot to determinate my mmr)....but what i found out ..i'm playing vs players who has low mmr then me ..so my team's mmr is higher the enemy's team ...that why i was getting +20 .... so can u plz fix the matchmaking ...or atleast explain why this is happening??