Hi there, please next time post support-type questions in one of the support subforums, thanks.
As a general hint and golden rule: Please only one problem per thread
You want to enable the _release and _updates media. See
https://wiki.mageia.org/en/Installing_a ... rrectly.3F and maybe
https://wiki.mageia.org/en/Mirrors_poli ... able_media for more information on that.
Please also check our
software management MAQeia for more information on software and package management.
You might also want to look at some articles on
https://wiki.mageia.org/en/Documentation especially from the beginners section, as there first steps for many
desktop environments are covered.
For KDE and GNOME, there is no "better" support or favorite, although I'd say most people that are active on the forums
either use KDE or some lightweight desktop. I also prefer KDE as I personally don't like the attitude/approach of the GNOME project, but that is merely a personal preference.
Others may prefer GNOME as it might be more streamlined, and should simply work. You have to find out for yourself what suits you best.