First, just to be sure: you did install texmaker via the software center right? If I got it right, you're coming form Windows world, and an habit to change in Ubuntu is the google/download/install cycle.
Sorry, I don't use greybird, so I didn't recognize what toolkit that would be for. XFCE uses gtk, but texmaker uses qt. This is why the theme(s) you select for xfce have not been (fully) applied to texmaker.
This creates a .ini file and allows you to save it anywhere you like. You can then manipulate this file use this page page as reference copying and pasting which is what I did. Make sure you only use texmaker code if config texmaker and texstudio if texstudio.
I'm considering your suggestion to reinstall entire system, because I'm having strange problems also with installing emacs and texstudio, and this things have never happened before. Aside of this considerations, your last suggestion DID IT, texmaker it's working now! Thanks a lot for suggestions and time you've dedicated to me! Best regards!
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