Learning hammer

It's become apparent that what I can do by importing from sketchup to hammer is very limited, and that i'll need to learn to create in hammer itself if I am to make anything of worth for garrys mod. It is possible to create more complicated geometries with hammer, inducing arches, loops, and tunnels. Here is that same box from earlier with some additions made in hammer. You can probably tell just from this screen grab that hammer is stupidly complicated to learn.