Update:
The two bolts on the brake booster that goes inside the firewall by the brake pedal all line up correctly. I was abled to tighten the nut on the bottom right side facing me. However, the upper left side thread with its limited space/movement for the nut to tighten on the thread/bolt, is a pain in the butt. I tried to line up the nut correctly on the thread to turn using the long extension with the 13mm socket. There is too much blockage from getting to the thread/bolt of the brake booster, except that metal bracket that goes through the hole to gain access to the thread/bolt that I was abled to extract the stripped nut previously.
Even though I was able to extract the stripped nut earlier, due to more room inside the 13mm nut, in comparison to a smaller hole 13mm nut trying to screw on the thread of the bolt on the brake booster.
I used peachparts brake booster removal guide (
https://www.pelicanparts.com/techarticles/Mercedes-W124/83-BRAKE-Brake_Booster_Replacement/83-BRAKE-Brake_Booster_Replacement.htm) and the picture shows both red arrows locating the brake booster bolt/thread inside the firewall. However, nothing is like that on my mercedes shows in front of the picture that is blocking from plain view of the upper left bolt/thread from accessing in order to get the nut in See the pictures below:
What is this bracket holding this thing that is blocking the way for me to access that upper left bolt/thread on the brake booster? Is there a way to remove that bracket? Or to remove that thing inside the bracket? I tried to use phillips screwdriver but both screws will not move and possibly stripped the phillips head of the screws. Anyone out there can help me out with this issue? Feedback/advice/comments is greatly appreciated. Thanks to all for reading/posting comments on this thread.