I hate to tell you this becaues I know how it feels to learn it, but you have the wrong basic approach to TF2 mapmaking.
You're approaching the task like some sort of god. You create a giant plane of ground, you drag it into a shape you think feels natural and you then proceed to scatter trees and houses on it. This may feel logical, but it isn't how mapping - at least not TF2 mapping - works.
I would say TF2 mapping is about using various basic shapes to construct areas that direct and control the behaviors of players in a way that makes combat enjoyable and balanced, then arrange those areas in a way that gives the entire map balance, intuitiveness and flow. What those basic shapes represent doesn't matter until you start detailing the map, something you shouldn't start bothering with until the gameplay aspect is more or less done. If your gameplay needs an inclined surface, make an inclined surface. When you get to detailing you can choose to turn it into a ramp, a flight of stairs or a natural slope depending on what fits best, but until then you don't need to worry about it.
Here's what I suggest you to do if you want your map to look and play more like maps made by good mappers, and also like maps made by me:
- Scrap your current map completely.
- Read a bunch of design theory tutorials here on TF2 maps, especially that stickied one about common beginner mistakes.
- Open some official maps in Hammer. There are a few ones that come prepackaged with the program, the rest can be downloaded
here. Deselect 'Tool Brushes' in the vis group menu. For your purposes they are only in the way, and they make everything look so complicated that you'll get a minority complex. Once you've done this, fly around and take a good look at how stuff is made. Select displacements and destroy them (as long as you don't save the map afterwards it's no problem to mess up stuff. If you save it's not really a big problem either, but it will make future reference studies more difficult) to see what kind of blocky shapes they're made of. Select various things (walls, doorframes, entire areas of play etc.) and see which proportions they have.
- Plan your map design on paper. Try to keep the roles of all classes in mind to give them all an appropriate amount of both opportunity and limitations.
- Build your new design in Hammer. Most mappers use development textures (filter: dev) for everything at this stage because they are plain and distraction-free, and they work as a convenient visual clue to playtesters that the map is an alpha. I guess you can use other textures if you feel like it, just don't put any effort into making things pretty.
- Submit the new map to a gameday.
- Get told by everyone, especially Wilson, that your new map is a horribly broken abomination.
- Repeat ad nauseum.
Good luck!
EDIT: Hey, that's a pretty dignified 100th post.