When the back window of the house is open, you can see the grave. Is it good at feng shui?

It depends on the distance. Generally speaking, good is impossible, and there will be "bad" or "nothing".

If it is the grave of the elderly at home, no matter how far it is;

If you are a foreigner, it doesn't matter if you know it or not.

If it is the grave of a person who died within 30 meters, it is not good;

If it's an old man's grave within 30 meters, you'll be fine if you don't bother.