Yes, that works for me too. Thanks@Krake
(@Bluejanis: Ich würde die Antwort anders formulieren... nix gegen dein Englisch, aber das is bessa *g*)
A1: To solve the problem just duplicate the american.gxt language file coming with MTA and rename the copy to the language you had installed: e.g. german.gxt or frensh.gxt.