I took a look at the map, and it's not going to play well, at all. I'm going to try and cover the issues I see, but you're probably going to have to start over from scratch.
The first, and probably most glaring issue, is that the map doesn't have anything interesting about it. If you look at any official map, you'll see that there's a good amount of stuff going on - height variation, cover, health, ammo, crannies, valleys, flanks, chokes, and more. While height variation does exist in your map, you only really use it in two places. Official maps use it all the time (though there aren't just random height variances everywhere - every hill and valley exists for a reason). Height variances help create interesting gameplay and a map that's actually fun to play. By giving players height advantages, you can create environments that are enjoyable to move around and provide natural cover with the landscape. For general cover, try to use it to break up your map and to give relatively safe spaces for attackers and defenders alike. I could go on about this, but
Scale and Your Map covers these topics far better than I could. You'll also want a good amount of heath and ammo kits scattered around your map in locations that you think will provide strategic opportunities for players. Go into your map and think, if you were injured, where you'd go to find health or ammo - look at placement in official maps and improve your intuition. If you aren't sure how many kits to lay down, the map's wiki pages list the amount of each kit for the respective map just below the general info (
Doomsday link).
This article contains a great deal more info on the issues I talked about, and you should find it very helpful.
Moving on, you've done quite a few things which you should really never do layout-wise. Firstly, you have sightlines leading from red spawn to blue for practically every spawn exit.
These are things you should try to avoid at all costs, as these sort of sightlines create campy gameplay that isn't fun for anyone. Snipers dominate the battlefield, and the length of the sightlines in this example simply compound the issue. Besides those, there are also sightlines that stretch the entire length of the battlefield.
Try to avoid those. While mapping to avoid those issues, also try to avoid making the map super cramped - you want to have a few sightlines, but you also want to keep those carefully controlled. Cramped maps also have other issues, such as being disadvantageous towards scouts and limiting soldier/demo movement. With that in mind,
raise the skybox. The height it's currently at is far lower than it should be - try to make it at least 1.5 times as high as a good soldier can rocket-jump.
There are a few miscellaneous issues present in the map. Firstly, there aren't any resupply lockers in the team spawn rooms - add those. There is a glitch in how the SD rocket is set up, causing it to not accept the intel on the first try and rotate the rocket cap the wrong way. You don't seem to have any artificial lighting in the indoor area where the rocket is held - whenever you have an indoor area, add lights so it's not too dark. Work on color-coding the map more than you've done, with each side using their respective colors - the way it's currently set up will probably result in confused players on the battlefield. The stairs leading up to the intel aren't very smooth - add a playerclip brush around to smooth out the individual stairs into a ramp. Other than that, I can't think of much to say (though that doesn't mean there aren't more issues) - don't make a room for people to kill each other in, make a place for people to play in.
Links above:
http://tf2maps.net/threads/guide-scale-and-your-map.12605/
http://www.nodraw.net/2010/06/tf2-what-your-map-is-missing/
Other links you may find useful:
https://developer.valvesoftware.com/wiki/Team_Fortress_2_Level_Creation
https://developer.valvesoftware.com/wiki/Lighting
https://developer.valvesoftware.com/wiki/TF2/Creating_a_Spawnroom
https://developer.valvesoftware.com/wiki/TF2_Design_Theory
https://www.youtube.com/playlist?list=PL2KT0JL74Qff_c1WbqNi4K5yAmpWAUQlq
http://tf2maps.net/threads/article-stairs-and-your-map.8827/