Some comments on learning chess.
Don’t get caught up in opening variations. Strong players talk about nothing else because at their level it does make a difference. Below master strength, games are won or lost mostly by one and two move combos. Play the openings on general principles, develop pieces, control the center, castle etc…, with a sharp eye for tactics.
Don’t get too caught up in strategic or positional ideas. A strategic advantage rarely amounts to more than the equivalent of being up a pawn, and must be handled carefully and patiently. Most players do not have the skill or the sustained concentration to bring such plan to fruition and a will likely drop a piece while trying to play out their strategy. Tactics rule in most club games. You may be the Napoleon of strategy but if you can’t handle the street thugs you will never get to command.
Game your opponent. If your opponent is short of time, bury him in complex tactics. Perhaps even sacrifice a piece for an attack and let him drown in the complications. If you are short of time, exchange queens and any other pieces you can. If you are losing, try to exchange all the pawns too. He can’t mate you with just a Knight on the board.
Ignore your opponent. Many players trash talk during a game. Even if it’s friendly chat, this can really undermine your concentration. Don’t read what he’s saying. You can trade insults after the game.
Nothing more frustrating than getting to the endgame with a material advantage and being unable to force a win. As @ScotchYeti recommends, learn the basic endgame plays starting with mates and then pawn promotion. End game maneuvers are long sequences based on simple plans. Knight and bishop mate is over 30 moves! If you know the procedures then finding the appropriate moves is much easier especially under time pressure. If you don’t you will be trying to calculate 10 moves deep with 10 secs on the clock. Even the comps can’t do that. The stronger comps use a library of EG positions.
Once you get a feel for what a winning endgame looks like, you can start thinking about long term plans for your game. Most master plans are about getting to an endgame with enough advantage to win.
I am not familiar with your rating system. The most popular is the Elo system in which a 200 pt difference means the stronger player should expect to win 6/10 games on average. The club ranks, A,B,C etc are 200 pts apart. Play against players one or two ranks better than you and figure out their tricks. If you play much stronger players you will lose and not understand why.