You can group brushes. Press B to go to the Entity Browser, go to Func and drag "Group" to the 3D window while your brushes are selected. You can select the entire group with Alt SHIFT Left Click. You should right click on Group and favorite it though so all you have to do is right click on the 3D camera and select "func_group" at the bottom whenever you need it.
Never played CS:GO, so don't know how accurate this is. However, a little more detail around the map wouldn't hurt, still a good job for your first map. Just keep working on this map, instead of starting a new project and i'm sure it can look really good.
If you need help pm me . You need to understand why people and mostly youtuber dudes hate playing a map with t4m. No offense mate. Map is good looking. And t4m is cool and all. But it just makes the game looks like shit.. Trust me.
How does it make the game look like shit? I've never had any problems with T4M maps ever. What is the problem here?