What a great Settlers Level but a really tricky one. I needed a lot of trys to perfect timing, build order and have the rng luck on my side. It was very close and losing just one of my military buildings could mess everything up. The AI wont attack until you attack so in general you have enough time to prepare your final attack. There are multiple strategies to conquer the gate so under 50m should be possible.

I am playing the Gold-Edition using Dos-Box 0.74