Welcome! Unfortunately I don’t know Mendeley, so I can’t really help. You didn’t mention the Obsidian Help. It’s a good place to start:
https://help.obsidian.md/Home
And, of course, all of the plugins have documentation and you can find many solutions here on the forum as well. Using search, or just browsing, you will encounter lots of discussions about the information you want.
That being said, it is useful to create forum help topics for specific problems you are trying to solve that have not yet been addressed. Using Obsidian is a great way to learn it. YouTube videos can be extremely helpful. But in terms of building your system and understanding exactly how you can best use the many tools available in Obsidian, there is no singular answer.
I saw this yesterday, and thought it might be relevant here:
Good luck!