Sr please do help me out for my placement journey

I guys I am starting to solve the leetcode questions but it takes time that's fine but I want to see the solution which makes me understand the real concept rather than mug up things, so anyone knows which youtube any paid thing that provide a good contain which make mine leetcode dsa stronger with understanding the main concept, I don't want to jump off to code but rather want to understand on paper pen any one who knows a good resources please tell me about it

Also there are so many questions right there but which ones are valid ones to be solved for the placement oriented I am a bit confused

also in which sequence the questions need to be solved as | don't think solving in a serial manner would help rather some specific random pattern would have been easy to level up in a specific pattern is not it

Guys please give some guidance accordingly