Thank you very much! I “googleled” Gimble Lock and I found a video on YouTube, from Level Pixel Level, with examples about the this issue: https://www.youtube.com/watch?v=mCZItVfEtRY
I got it! I think understood your explanation now. But how can I use the ‘W’? How can I avoid the Gimble rotation with the WXYZ? Again, thank you very much!