Theese doors will not be affected by the physics in the game. You can set the number of degrees that the door will rotate aswell as some other nifty settings.
Nowdays making a level entirely out of brushes is impossible (if you want it to be good-looking). You are going to import models from third party 3D applications.
The reflective water is one of the best looking effects in Half-Life2, considering how easy it is to do it sholud be used whenever it fits as a decoration for your levels.
What you need to do first when starting to make levels is learn how to use brushes efficiently and manipulate them as you want. This is the build-stones of your maps.
This tutorial is made to give you the basic understanding on how to navigate and customize your viewports inside of Valve Hammer Editor to make your own levels.
This tutorial will outline how to make basic doors, these include; Rotating triggered, up an down triggered and pivoted physical doors. Remember this tutorial is for creating doors only, do not expect to be taught any texture based work.
In this tutorial you will be directed through step by step how to build a bridge. This will then be suspended by wires and constraints to become a object which hangs and reacts to physics.
In this tutorial I will walk you through step by step how to setup a dynamic light which will be parented to a physical object which will react acordingly when shot and moved.