Hi again, keep in mind you could try OnShape to create your own model, which is cloud-based and free to use.
The CAD mode is used to edit a model, not create parts etc. You can share the project you want to edit with me so I can see why the face is not deleted if you want. 
The flow volume extraction tools can be accessed by clicking on this icon next to the name of the model you want to use. It will appear when you place the cursor over this area:
