Hey, welcome to the site and congrats on getting your first map out there! That's always a huge first step!
I downloaded the map and ran around it a bit to give you my first impressions of it.
A quick note, we generally recommend using the site here for map hosting or Drop Box, as sites like Mediafire make you jump through extra hoops before getting the download. Every one of those hoops could potentially lose you a download!
Have you dont any player testing on this yet? I noticed you released it straight to 'Final' and didn't use any iteration on your filename (koth_container.bsp). This can cause some issues later on if you decide to do any updates. It's always a good idea to use some type of iteration (_a1, _b1, _rc1) for any release you do.
But as for the map itself, not bad for your first real TF2 map at all! Looks a lot better than my first, that's for sure!
I feel like you did a decent job taking every class into consideration, although it is a bit tight in places which might make close-quarters classes a bit overpowered at times.
The map is definitely very small, though. There isn't a whole lot of space between the spawns and the capture areas. I noticed you placed a second spawn closer to the field to help combat the spawn camping, but I feel like it's way too close to the capture point. You can actually stand
a few steps away from the resupply cabinet and spam Demo grenades right onto the capture zone, step back to resupply, and back forward for an endless stream of spam. This is a pretty nasty issue.
Personally I'd get rid of the extra closer spawn room, create a bit more space between the further away spawn room (A courtyard or something), widen that spawn, and add a second exit to prevent some spawn camping.
Some minor notes:
You did a good job with differentiating sides using team colored detailing. That is often forgotten by early mappers.
Your detailing over all is pretty decent for it being your first real TF2 map! Good job!
Your lighting overall is a bit dark in the center game space and a bit bright in the opposing buildings. You could tone down your HDR lighting.
These stairs are super steep. If I was trying to do them in this tight of a space, I'd cut the height in half, and then do the rest of the vertical distance with a second staircase 90* from these, with a small landing in between. If that makes sense...
You did some good things with your clipping, but there are some issues as well.
This might be harder to do in game without having the clip brushes visible, but it'd still be possible. If you want the beams going across the top to be able to be jumped over without being able to stand on them, you could always use a trigger_push just on the top of it that shoves anyone trying to stand on them off. You might want to hint at why this is happening if you go this route, though. Maybe rounding the top a bit or something.
You should either clip
these high up props or turn their vphysics off. They create a lot of high up perch points jumping classes can get to.
This route between the two containers is a really tight gap.
I like the detailing in your spawn room here!
This little detail area is nice and simple, but does a good job making that space feel more open.
Don't be discouraged by all the negative feedback! You made a pretty decent map for your first 'real' go at it, so good job! The most important part is to take what you learned from this project and either fix what you can or move on to the next and apply it!
Edit: I accidentally a lot of words.
