The world of Gothicus was significantly larger than the first game, featuring diverse environments from swamps to underground cities.
Verify the data folder name is correct and placed exactly in the Android/obb or Android/data pathway. Ensure it is not nested inside a double folder.
While some versions run natively, others might require a virtual machine (like VMOS) if your Android version is too high.
If you're interested, I can help you write a on sideloading APKs in general, or a guide to legally obtaining and installing classic mobile games where the developer has abandoned support. Let me know.
The placement path depends on the specific version of the game you downloaded: