SRAM GX Eagle AXS installation

Hi,

I am building a bike for the first time and I struggle with the installation of the rear derailleur.
I am new to AXS and always had mechanical shifting until now. Thought it would be nice to try and went for a mullet setup with the Apex AXS with GX Eagle rear derailleur.
So, I thought I had followed the SRAM manual well, but then I could not shift to the smallest cog and only up to the third largest. I thought I might need do the micro adjust in the app, did that, and now I can shift to the smallest cog but the image shows til where I can shift now 🙈
I did not adjust the B screw yet..thought this needed to be done with the tool and shifting to the second largest cog.
This can’t right, where did I go wrong? 🥲

Thanks in advance.

by PiPu1991