For a first map, that's pretty good mapping. But gameplay wise, it pretty much IS unplayable. ALL paths are linable (you can line and there's NOWHERE the enemy can hide) and the map is too straightforward. Also fix your textures properly. The lights on the bottom floor on either side of the ladder for instance.
Overall, it's a decent effort for a first map, but like all of us mappers say, try not to release your first few maps. Practice more and you'll do fine.
If you still want comments on how to fix it, here are some.
1 - Again, align your textures.
2 - Make the hallways on either side wider and put some obstacles in it. At least when someone's lining, there could be something you could duck behind.
3 - Fill up the middle bottom floor. Obstacles, barrels, boxes, whatever.
4 - Looking down from the towers, you have a LOT of empty space between the bottom floor and the top. See if you can add anything there.
5 - I'm guessing the water surrounding the towers is the moat? If it is, I suggest you make it a dirty water texture. I didn't even know it was water until I fell in.
6 - As long as there is one person camping the tower, there is ABSOLUTELY NO WAY to grab the flag and make a run for it. NO WAY at all. See if you can come up with a solution to fix that.
Hope those things helped you a bit.
