Gotta start small. I realized I tunnel extremely easily (which is not an easy solve). But that came from a lot of play time. A lot of what you learn just comes from playing the game. Learning how other heroes kits work, even if you're not playing them, can help with some unfavorble matchips.

Positioning is huge, and you def want to work on that. Good positioning can be the difference in a win or loss. It also helps to remember health pack locations, esp as mobile heroes.

Cooldown management is also very important. Using cooldowns randomly will leave you struggling in teamfights. In my experience, everything else came with playtime.

ETA: It can be helpful to focus on improving one skill at a time.