The server has problem with spezial characters in notifications and the language selected in the setup is only applied to the client server is in English.
Server is currently always in English, there is no server language setting yet. The log file (if enabled) will always be in English, to make sure it can be read and understood by the developers 
I dont mean the log file. I mean the part of the server that is displayed as a windows background process. That contains all the options and settings.
Got it, I forgot that I already added a language setting to the popup menu, the weird characters is probably an encoding issue, Traintastic’s languages files are UTF-8. I’ll have a look.
Fixed it! → [trayicon] fix: notification text encoding issue. · traintastic/traintastic@be5d081 · GitHub
I also corrected the typo in the message.
I’ll look into the setup tomorrow.
I’ve checked the setup, it will also set the server language to the language used in the installer, but only if there is no settings file yet. So basically only on the first installation, for updates it is left as is.