Open a konsole, run gimp from there. Specify the image file you want to open.
Example; gimp mypic.jpg ( assuming you are in the directory where mypic.jpg lives. If not, add the path to the .jpg in front of the .jpg. 'gimp /path/to/pic/mypic.jpg'.
Either way, it should work. If it does not, cut and paste the error information into this thread.
I use Magia, if it is installed correctly, I have found it very stable. I don't like the way Mandriva has gone, I used it for years, from the Mandrake days; 9.0 up to recent releases.
when I ask people who know about linux I get criticized for not knowing enough, that is a tough one.
It takes time to learn anything new. You have to decide if it is worth perusing, or not. If it is, keep trying, asking questions, reading, you will learn over time. We have all been there.