Ok, I see I have asked to quickly.
After looking a little more into this, the solution seems quite simple.
In my child themes style.css I added these css rules:
.sidebar #primary { width: 70%; }
#secondary { width: 30%; }
These rules makes the right sidebar 30% wide and the set the main content area to 70% (it needs to be 100% together).
Seems to work fine 🙂
Have a nice day! Cheers
Hi MrSlartibartfast
Thanks for reaching out. That’s correct! Those two rules used in your child theme style.css file or in a custom CSS plugin like Simple Custom CSS are the way to go.
If any further questions come up, please, let me know.
All the best.