I tried to clean it with oven cleaner, with the green side of a sponge and I tried several cleaners without success.
the whole glass was like this brown spot.
I want to show you, how easy it is to clean the glass.
It is helpful to remove the door before u start.
in most cases this is easy, just half open the door and pull it away from the hinge.
if u have doubts, take a look into the manual of your oven.
Step 1: What You Need
-a sponge or paper towels
-a dishwasher tab
Step 2: Cleaning
You will see how easy and fast it is.
And the best, the glass doesn't get scratches.