This is an excellent question. Besides a variety of outside learning resources, there are a number of Aptech sponsored resources to help you learn GAUSS.
Aptech has an active Data Analytics blog which is available at https://www.aptech.com/blog/ .
There is a GAUSS YouTube channel with a number of videos available at https://www.youtube.com/channel/UCEqiDEVdxKIqVFYs4kOGCZA .
Finally, you may also want to preview the User Forum for answers to specific questions at https://www.aptech.com/questions/ .
If you have any questions about accessing any of these, please feel free to contact me at [email protected].