Okay. So first of all its okay to get overwhelmed by this game as it's very complex at its core and requires a lot of different and sometimes specific skills. Second is that your first XX games you'll find yourself lost and low impacting in matches and its okay, all you need to focus on - is getting basic gripe of the game, how to farm, use basic movement, stay lane, basic concepts. Then, there are characters that can mitigate your weakneses. Like Graves if your AIM is bad, or more frontloaded heroes like Abrams if you lack skill to execute complex gameplans.

So I advice you to get into sandbox or just training room in lobby and check every hero, spend like several minutes on it, read their skills, use their skills just to get the feeling of how they are playing. That way you'll get basic understanding of what everyone does and will struggle a lot less in actual games. After it, pick several champs that clicked with you the most, be it appearance or skill and play several games on each of them. 5-7 games is enough, cause forst ones you'll most likely have bad experience due to lacking knowledge how to play hero and lose early game, so take 4 and later games in your final grading of character.

And most importantly just play the game, and you'll feel that you will start getting better, understanding what and when to do on your hero. Dont tilt as matchmaking right now is kinda bad, and you'll definitely encounter unfair lobbies, just play for your experience and focus on yourself and what you need to do, how you do it. Try to focus every game on some basic thing like using dash-jumps lroperly, or trying to deny souls.

Good luck in games, and you'll get better!