3D Graphics is a huge subject and provides an opportunity to solve an infinite number of new problems on top of all the millions and billions of problems that are being solved using 2D.
If you are developing a project and are stuck with some issue you cannot solve, I recommend asking your question on the Threejs Forum at https://discourse.threejs.org/
I read it every day and sometimes answer questions if nobody else beats me to it.
When asking a question, it is useful to provide a screen grab and/or a working example demonstrating the problem.
You can use sbedit.net to edit and generate a share link for any of the working examples on this website. Press the <> button at the bottom right of any working example to open the editor, make your edits, and then share.