P. I installed the KDE desktop, but my preferred applications: Iceweasel and GIMP look horrible how to fix this?
R. In order your GTK+ 2.x and GTK+ 3.x applications have the same appearance as the native KDE applications you should install the following packages.
To do this, type the following command in Debian GNU/Linux
sudo apt-get install gtk2-engines-oxygen gtk3-engines-oxygen kde-config-gtk-style
1. Start Menu
2. Select System Settings (KDE 4) / Settings > System Settings (KDE 5)
3. Select Application Appearance
4. Set the options shown in the figure below