Analysis


You should be looking for why the said 'best move' is a good move - pin the reasons down (for example, It allows counter-attack opportunity by allowing f5 to gain a tempo while stopping the attack on c2). THEN, see how you can improve your own moves. This is the baseline in what you need to know, there are WHOLE chess books dedicated to analysis and theory.
Look for mistakes in your own game. Mini-differences like .3 difference between your move and best move aren't as important as say, a full point's difference. Hanging material, tactics, search for these opportunities.

Here is the way I do it:
https://www.chess.com/blog/nklristic/how-to-analyze-your-games-first-steps-to-chess-improvement
In short, what you don't understand, try to figure out with the use of the engine. If the evaluation changes slightly, in many cases you will not be able to pinpoint why one move is better than the other.
At lower ratings it is most important to understand greater swings in engine evaluation. Sometimes it will be a straight up blunder and you'll see it, sometimes it will be due to some missed tactics which can be more difficult to find. Anyway, find out what you can, what you don't understand you can ask in the forum, but other than that just forget about some unclear engine line.
Remember, even strong players doesn't know everything, and even stronger players might not understand some engine move.
As you study chess, you will figure out more and more.
Its difficult because your analysis is only as good as your ability. The more you play and study, the better you get at interpreting the engine. My suggestion is dont worry too much about the moves you dont understand, instead look thematically at the ones you do understand and what it is telling you to improve. So if you lose the game because your opponent went up a piece due to a knight fork, then this tells you that you have trouble seeing knight moves so should go and drill knight fork puzzles. Its easier to see and fix that weakness than understand and remember that you should play d4 and not d5 in some position.

Thanks for asking the question. I also have no idea how to analyze and have difficulty seeing what is going on in analysis by others.