Someone please tell me what I am doing wrong

TL;DR QQ my team sucks i am god but my teams are holding me back..........Yes that's what most of you are going to read below, but I know that I am not perfect, or even a good player, im in bronze for a reason, but i am trying to get better. I'm just trying to figure out what I am doing wrong or what I need to do different to help carry my team so that i don't get demoted again.

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Now, I know that I am far from pro, I am probably not that good at all. If you look up my ranked history you will see that i do have some bad games of my own where I get seriously outplayed, but you will also see games where my score is bad and it was not bad before the game got near its end. This happens because the other team gets fed hard by trolls or because we are 3/4v5. I am not claiming that I am good enough for gold, not even saying I'm good enough for silver, but i have proved consistently that I am better than b5. In one day i promoed to B4 3 times, then lost the next 5 games (or 5 out of 8 games at best) due to afks or intentional feeders (yes i differentiate between intentional and just unskilled). My trouble seems to be that once i get promoted into B4, my next few games are trolled (either 1 or 2 afks, or an intentional feeder) and i get demoted back to B5, hit another win streak, promo to b4, then trolled again.....rinse and repeat.

It seems that the common attitude of people above bronze is that "if you are good enough to get out you will be able to carry your team to victory often enough to get the points you need to move up" Ok, I can accept that if that is true, but will someone please tell me how I am supposed to carry 75% or more of my games when there is only me and 1-2 other people that are playing well enough to do so. If I could just get into B3 or even upper B4 i would not be QQ'ing here. If there is something I am doing wrong or something I am just not doing that i should be doing I would be ever grateful if someone here could help me figure out what that something is. Do more than look at my history and make a decision though, come play a game with me, custom or norm, and see how i play. Or spectate one of my games even and tell me how i am supposed to (on my own, or with 3 players) beat 5 man teams often enough to progress. (it seems to be rare that the troll is on the other team, (although that is statistically improbable).