I'm a PS user so I can't really help with GIMP, but right now I suspect that even a fellow GIMP user might have trouble helping you.

If you could attach some examples of a) what it is you're trying to accomplish (i.e. link to the tutorial you're trying to follow) and b) what happens when you try (screencap of what the result is). Also a description of how you are going about it, what keys you press and what values you are inserting when you have to insert something.

It's a little hard to figure out what is happening from just a description, or at least it is for me. Hopefully you'll get the help you need, I know how frustrating it is when you have a problem and can't figure out if it is you or the software that is causing the issue.