Adam111777, you are wasting your time. They will believe what they want to believe. I have personally flew over the Antarctica. When I say over, I don't mean I skimmed the edge. I flew OVER the Antarctica. Granted, the plane didn't flew directly over the south pole, but we were probably a couple hundred miles from that location. There was no 'edge of earth' or a 'wall off ice' stopping water from falling off.
These people will have a rolodex nonsense answer/response for everything. They will try to twist everything you say to support what they believe. I honestly believe most people who purport to be flat earthers are just trolls - and apparently succeeding.
Bottom line is this. The earth is a globe. Even if you don't trust the government or NASA, you can trust trigonometry. Just use sohcahtoa (a trig term for finding unknown distances in a triangle). You will see the sun is about 93,000,000 (not 3,000) miles from the earth. You will see the moon is about 250,000 (not 3,000) miles from the earth.