My OLL knowledge is ok i guess. but 21 PLL algs for me is brutal to remember. do you have any suggestions on how to learn them if not how did you learn them and what problems did youencounter
I suggest you learn 1 a day, and spend like 30 minutes going over it, then the next day practise some more, and when you get the case always use the algorithm.
OLLs have 57 algs, but you say you're decent, but 21 PLLs is hard? You must mean 2-Look OLL (7 new algs).
Look at the algorithm, examine possible patterns, and perform it many times to get the fingertricks. The next day learn a new one, but practice the previous one, and build up from there.
If there is more than one similar algorithms (2 A's, 2 U's, 4 G's), I recommend you learn them together, in groups.