@larens It looks like your Windows username has non-ASCII or Cyrillic characters in it which the FAF client can't read/write to.
What you'll need to do is either create a new folder for where FAF will store your maps/mods, such as in the FAF Data Location itself (default is C:\ProgramData\FAForever), a folder at the root of your main drive or on an external drive, & then go to FAF client > top left menu > Settings > Forged Alliance Forever > Maps and Mods Location > Choose... & select the folder you just created or select an already existing folder that isn't located within your Windows user directory.