nice question~!

i have always been using naver dictionary app. for more complex stuff i use google/naver/daum with ‘[insert word/phrase] + 뜻 or 의미 or 영어로’ and click the ones form websites like hinative, itaki, wordrow, naver blog, tistory and reddit (basically anything that looks legit and then just deep dive 🏊‍♀️) when there is suffix/prefix that i don't understand i look it up by using keywords ‘[insert prefix/suffix] grammar’

hope it helps!