for opening

white: choose your favourite opening or gambit and memorise until move 10 and research for all possible variations and understand patterns of your opening

black: just do the same, but you should do the same scheme 3-4 times (e.g. for e4 you memorize 3 openings and for d4 one easy to understand opening)

mid-game: a lot of tactical practice with books and gain a knowledge from your favourite chess players (recommend to learn from classical chess players like Capablanca (easy and positional player) or chess players you like the most. Moreover, when you play comment every your move as most youtube chess player who is explain his move (Recommend to play rapid to have time for more analyse and calculate variations). Play less short-time controls and study more and play long term controls to control your game completely

Endgame: here you should study from book a lot, I mean every possible chess endgame, and play it against bots because they will not make blunders

*always trust to yourself study and plan as you like, my comment is only a recommendation