You maybe interested in buying a book (I did, I didn’t read the whole book but I learnt several things from it) https://www.sketchup.com/learn/resources
This is a very interesting site I recommend you keep in your bookmarks.
It has different kind of information interesting as for example some problems you can find when you work:
At the point I am (there is still too much to learn) I recommend the following tutorials, mainly the first 4 (you can ignore the ones about the programs and tools you’re not interested in this moment, as for example the ones about LayOut or the ones about certain tools as for example 3D Text, all of this depends on what you’re interested in).
When I have a trouble or I don’t know how to get something I take a fast look on YouTube or Google if I don’t get an answer then I open a thread in which:
- I describe my doubt or issue.
- I attach screenshots if it’s necessary.
- I attach a .gif if I need to show the steps I’m following (You can download LICEcap to do this, it’s amazing easy).
- I attach my .skp file
https://forums.sketchup.com/ and https://sketchucation.com/forums/ are good choices.
In the following site there are a bunch of exercises using AutoCAD the ones you can do with SketchUP (they’re not only 15 as they’re sown in the link, there are lot of more), but they’re in Spanish, I’m from Spain if you need help with some exercisse or if you need a translation, let me know, I’ll try to take it a look.