1.What interest you at the moment, especially supplimented with less advanced books first like Understanding Chess Endings.
2.Take more time solving them, change your approach to them, make changes to your thinking system, or admit that you're relatively weak in endgames and tackle less advanced problems first or else the problems will be spoiled. Most of the problems are just from compositions anyway.
Hey guys,
I finished the first chapter of the book (Pawn Endgames).
Thanks for your advice!
(Btw I'm almost 1900 ELO OTB, if it helps)