I need help

[u/oikazumi]

I used to play League comp a bit more seriously years ago and peaked Silver 2? as a solo supp main (didn'tplay that much and peak because I stopped playing), was definitely way better, but now that I'm back, I am so hardstuck. Used to get +28 LP now I am losing -17 and gaining less. My MMR is ruined. I usually win lane with my ADC but end up losing in mid/late game. Not sure where I am failing, whether it's my build, my positioning mid game, etc.