The different between Would, Would have, Would have had, Have had.

Would use when you want to express our preferences, desire, opinion, or to making a polite request.

Example for polite preferences "I would like to go to the beach", "I would prefer a chocolate".

And another example that I came up with was "I would like to be a better person", "I would think that you should been started watching HunterXHunter".

And a tip for saying I would we will say just I'd.

Would have it a unreal situation that doesn't happen but if it happen then this situation might happen.

Use Would have + participle or Would have + continuous (been ---ing)

And I had seen this example and I thought it was so complex.

And this is the example from this video

"I would have been doing better in school if I had been sleeping better, but I would have been sleeping better if I hadn't been worrying so much about school."