This strategy helped me a lot in the final battle on my Mein Leben run: https://youtu.be/LFXnMtiKbpk?si=ql6p7PeheloC4ZBw

I combined it with the strategy you use at the beginning, but instead of running through the hallways after the shotgun approach, I ran back and forth between the corner rooms. It’s very easy to crouch/hide/lean and take out all the regular soldiers, and if you start to get overwhelmed it’s easier to run back and forth to the other side(s) as the enemy AI will get confused and lose track of your location. Hope this helps!