Problem with custom Font (with ÄÖÜ) for existing game

[Taktloss]

Hello together,
i try to make a Fan translation for Technobabylon and even wrote my own application, it creates TRA files. However everything worked fine except that special characters like Ã,,ÖÜàŸ didn't show properly. I tried to put some custom ttf into the game directory but then i get a error message "Unable to load font 0, no renderer could load a matching file". Then i did put a default AGSFNT0.WFN in the directory, the error message did go away but it uses only the WFN file now and still no special characters and if you remove the TTF file the WFN isn't used too !?. Then i did edit the WFN file with the WFN Fonteditor and did extend the font to 256 characters and did add ä as 0xe4. But still no luck now i'm not quite sure what else i could do to fix that.

And does someone maybe know why there needs to be a TTF and WFN file even if only the WFN is used then ?

I really would apprecite some help if possible

PS: AGS version of the game is 3.3.0.1164