I’ve never used MonoGame Forms, but I think you should make GraphicsDeviceManager graphics a global variable so you can reference it throughout your program.
After that, in your Game1() constructor, not Initialize(), put your other four lines of code.
Two more things:
You should be able to remove the *s around the word this, I haven’t seen that before and it could be causing an error.
base.Initialize(); should probably go at the end of your Initialize() method, just to be sure everything gets initialized properly. Same applies to your Update() and Draw().