If you have a German game and keybord, simply type "mücke" on the status screen (B). Make sure none of the keys are assigned to the status screen (C is by default). Otherwise:

• Download this: https://www.speedrun.com/tools/Demo_Devmode_ggr3o.rar
• Go to your Gothic 2 Demo folder and place the gothic.ini in the system folder.*
• Start devmode.exe. (Or install AutoHotkey and use devmode.ahk.)
• In the game press Ctrl+M.
• Try if it worked by pressing F8.

*Or do it manually:

• In your Gothic 2 folder enter the "system" folder, open "gothic.ini" and search for the "keyboardLayout" entry and set it to: keyboardLayout=00000407
• In the control settings, make sure B is bound to the status screen and neither M, C, K nor E are bound to it.