I'm stupid, all I can do is make boxes.

I’m new to Hammer and when modeling all I know how to do is make simple boxes. How do you curve something? Like make a curved wall/tunnel.

Vertex manipulation tool and the clipping tool.

Arch tool. Same tool you use to make blocks, but then over on the right there is a drop down box that reads “block” change that to “arch”. Also investigate the vertex manipulation tool.

Thanks, I won’t release any shity maps thanks to you.

Well, while he did help, that’s not going to make your maps good on its own. If you really want some help I suggest looking at these sites:

http://www.halfwit-2.com/?page=tutorials

Those have a whole lot of valuable information, notably the last one, and a lot of good tutorials, really only the first two though.

Also displacement, spike, sphere, cylinder, and arch.

You can make decent maps with blocks, they’re just harder and you have to pay more attention to fine details.