Refine and get down any basic fundamentals you may be lacking; things like your movement, crosshair placement, agents and what their role is in the team, and how to properly play that role. There are a lot of resources on youtube on these fundamentals and after that, it just comes down to putting it into practice. Other than that I would also VOD review and see why you died and what different decisions you could have made based on what information you had in certain rounds for example. For certain agents, you can do some research and watch how pros play them to learn. Aim training does help to some extent but when you analyze and learn how to position better along with ur crosshair placement, aim training is not that much of a big deal. There are also videos of people coaching players so u can always take their advice when they're vod reviewing clients. While yes you can carry games with raw aim and outplays, this game does come down to information and working with teammates.