This is a pretty neat little map! There's some really cool ideas in here, but I think there's also some things that could be improved. You use drop-downs and one-way routes cleverly, but there are lots of places where there are only a few routes. Generally it needs a bit more width, if you get me? More ways for both attackers and defenders to go sideways and around the other team, plus wider main routes so you can dodge a bit - in the current spaces, they'll be hopelessly cramped and spammy for full teams of twelve! I would suggest at least one way to get from each area to the next, and make all the big areas - the start, the route between first and second - about 1.5 to 2x as big.
The final part looks quite easy to take: there's no raised areas or good places to defend from, or for snipers or sentries to set up.
Also, whatever custom thing you have in the first area isn't packed.