So, I can't get throught the main gates without getting slaugthered, any tips?

The frontal walls have a blind spot, and there's a specific hill they can't hit behind. Position your archers there and you can pick off the first line of walls with impunity. You may need to save/load because you have very few archers and if you step outside of the blind spot you'll be turned into a pincushion very quickly.

Thank you