Looks like you're new, so part of the issue may be that you aren't sure of what every champion can do. Since you're just starting in normals, this is expected. CSing well is just something that comes with time and practice. Just practicing the game in general will help you the most at this point.
I also main ADC and have been playing it since last season. There are a lot of things that are important to the role, but since you're just starting out and are level 7, you should just focus on not getting damaged as much as possible by the enemies and hitting all your CS as well as putting damage onto them if you can. Another thing - and maybe why you started off well and slowly started feeding. Are you looking to see where the enemies could be? I know lots of people don't ward as they are learning, but just try to stay cognizant of where the others are.
If you have any questions for me, feel free to ask ^^ I am on NA, or I'd play with you and help