I would like to work on some wonderful excercises (not particularly hard) in ring theory, subjects PID, UFD or polynomial rings. Can you introduce a resource that has newer exercises? Or if you can remember a good one, please let us know about it too! :)
Thank you very much!
There are lots of places to find exercises. Any general algebra textbook worth its salt will have plenty of exercises on ring theory (in particular the subjects you've named).
Off my bookshelf, there's (in approximately increasing order of difficulty):
Again, though, almost any algebra book will do. All three of these are available (perhaps unscrupulously) in PDF form online, and (for better or for worse) complete or partial solutions to many problems (certainly from Dummit and Foote) are available on this website. You might also have luck looking at Number Theory textbooks (though I don't know much number theory, so I don't have any recommendations).
I hope this helps ^_^