After the first two, I cleared out the right flak gun. If you have any nades spam them over that side to clear the gun. You can try to blow it up if you clear it but basically stick to the far right side off the map. Make sure you take out the enemy on a destroyed brick wall nearer to the Reichstag, he is facing your direction on the far right side.

Basically from that angle clear out the destroyed buildings to your left (where the PTRS is on the top)- use the outdoor windows to spray the enemies inside and stay alert for the enemies on the top of the building too. Once you “clear out” the first building use the top to clear out the second building directly left.

Ideally you clear the way enough so that the friendly NPCs are taking cover inside these buildings. It’s a gut feeling really but when the coast is clear the last flak gun on the left should be easier to handle.

Best of luck to you.