How does competitive matchmaking work

Hey, so I’ve recently dropped on my alt from 3.4 to 3.0 in competitive, because of SHlT teammates. I’d like to know how this works so I can win games and climb. Also I mean it, I’ve killed 4+ in games and still lost team fight. Jeff can you boost my competitive sr or how I get placed in games where there is a huge difference between teams. Teammates throwing vs 4.6k smurfs or just normal diamond players but my team throws ty

Here you go: