Can I get a detailed description on how the MMR/LP system works?

Okay so last season I was bronze 3 (started ranked in September or October I think of that year).

This season I was in b4 and got demoted to b5. My MMR was at about 980 before the demotion and then 950 after losing a FEW games (not just one). Keep in mind that my LP win/loss is +22/-17 even though I'm less than 50% WR and my MMR is average. So I get demoted, then the next game I win I get +23 LP (which probably means my loss is -16 now) and my MMR goes from 950 to 1001. So my MMR went down by 15-16 per loss but up by 50 for a win. I also have issues where my MMR goes down on wins and up on losses (not by this much but it still does). I've looked at the ranks of other players in each game and they are all b5-b3; nothing really changes that much from game to game.

So I'm really confused and the system seems really random. Because I thought the game was supposed to reward your winning streaks with more LP gain since your MMR would be much higher. But mine was average (now it says it's higher on op.gg) and I still got +22-23 from each win and only -17-18 on each loss.

Help? I'm not that fixated on this but it's nice to monitor my progress and I would like to know the system better.

Thank you!