Don't just focus on aim and lineups. Gamesense is the biggest factor in getting you to immortal. Every time you die, or lose a round. Think about exactly why you died and how you can fix it. If the answer is frequently "aim", that's an indicator that you're taking bad fights, not necessarily that your aim is poor. Keep doing that and eventually you will build up a bank of scenarios in your head so you can play rounds much better.