I'm trying to make a basic 3D visual flight simulator that displays terrain and buildings in 3D from the cockpit's perspective. I don't care about the flight physics. This project needs to be completed in a month or so.
The end goal is something like this: 
Except with buildings and vegetation and other structures. What framework should I use for this?
Other than a time machine so as get a lot more time than 1 month you are going to need something that does it all for you.
I would suggest using the Godot game engine. The actual development language can be C++, C# (using Mono), GDScript or one of the community supported languages.
I recommend starting from the manuals Getting Started step by step guide.
