@Rowin-Side
I digress on your opinion that age makes it harder to learn better chess skills. I think it takes more effort, but not enough to be disheartening.
Plus I think older people do well by repetition of problems.
Do hundreds of mate in ones
Then
Do hundreds of mate in two's
Pattern recognition is important, so doing problems that target different stages of the game is key.
After you get pretty good at those, then start doing tactic puzzles... start easy and ladder up to harder problems.
Finally start doing combination problems, which are similar to tactics, but start with a key move instead.
*Chess Compositions is the same thing, but in a combination problem, the position comes from an actual game.
After that, one could start thinking about more specific training like learning new openings, endgame training, etc.
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*because Chess Compositions are constructed, the vast majority of them are exceedingly difficult.
Combination problems can be generated by a computer program looking at a chess database, so the problems can be limited by variables like rating level of the players, number of pieces on the board, etc.