I'm recently having interest in solving problems like the ones in here but as the problems are not that familiar I can not efficiently think of the solution or the concepts.
Of course have solved some problems before and understanding the concepts of the problem when the problem is general or a little harder but these kinds of problems are too unfamiliar and hard to find proper sources discussing these kinds of complex problems.
What books are recommended for meeting and solving such kinds of extreme problems?
Have you tried searching up the mathematicians who proposed these questions and seen if they had written books such as this?