Most of us have, and no curvature of Earth is observed. You will likely find even honest Heliocentrists will admit this when pressed. However, their excuse usually is that the planes aren't high enough to observe the Earth's curvature (rather than ours, that the curvature doesn't exist for us to observe it).
Also, if there is no curvature then you can see every boat on the ocean with a telescope. You cannot do this because there is curvature and this curving causes things to become out of view.
Answered in a different thread. However, perspective and the atmosphere not being completely transparent are the reason you can't see every boat on the ocean with a telescope.
All of the other planets are round. Why would Eart be disc shaped. Look at literally every other planet.
Earth is not a planet. It is the Earth. Why should Earth's shape have anything to do with the shape of the planets and stars? Note also that you shouldn't make the mistake most Heliocentrists do when debating Flat Earth, in presuming Flat Earth believers adopt all Heliocentrist assumptions. They don't. Some main differences are the stars are relatively close, the sun is not nearly so large as in Heliocentricity, the sun and moon are not nearly so far as in Heliocentricity, the sun and moon orbit the Earth and as stated, Earth is not a planet. Note that the origins of the word "planet" come from "wandering star". The planets are more like "wandering" stars than "Earths".
Because you seem to be new to the subject, I have explained some of the basic differences between Heliocentricity and Flat Earth below.
Why does the Earth seem motionless?
Flat Earther: Because it is motionless.
Heliocentrist: It only seems motionless because it's spinning at a perfectly uniform speed with no acceleration or deceleration ever and the atmosphere is magically velcroed to it. Actually the Earth is spinning on it's axis at 1,000 mph, rotating around the Sun at 67,000 mph, which is orbiting the Milky Way at 500,000 mph and shooting through the known Universe at 67,000,000 mph. We don't feel even the slightest bit of this motion because all the centrifugal, gravitational, and inertial forces somehow perfectly cancel out.
Why do the Sun and Moon appear to be the same size?
Flat Earther: Because they are the same size.
Heliocentrist: They only appear to be the same size because of an incredibly perfect parallax perspective from Earth. Actually the Sun is 1.392x10^6 km in diameter and 1.496x10^8 km from Earth. The Moon is 3474 km in diameter and 384,403 km from the Earth. And these just happen to be the EXACT diameters and distances necessary for a viewer from Earth to falsely perceive them as being the same size.
Why do the Sun, Moon, and Stars all appear to revolve around a stationary Earth?
Flat Earther: Because they do.
Heliocentrist: The Moon does revolve around the Earth, but the Earth actually revolves around the Sun, and all the stars only seem to revolve around the Earth because the Earth itself is spinning beneath your feet!
Why do we never see the rotation of the Moon?
Flat Earther: Because it doesn't rotate.
Globalist: Both the Moon and the Earth are actually rotating but they are doing so in such a way that from our perspective it seems that neither are. The Earth is spinning East to West at 1,000 mph while orbiting the Sun at 67,000 mph. The Moon is spinning West to East at 10.3 mph while orbiting the Earth at 2,288 mph. These motions/speeds perfectly cancel out so that the Moon always only shows us one side.
Why do the stars appear to be fixed along a celestial hemisphere?
Flat Earther: Because they are.
Heliocentrist: The stars only appear to be fixed along a celestial hemisphere because they are so incredibly far away. Even after hundreds of millions of miles of our (supposed) orbit around the Sun, the stars appear in the exact same positions at the exact same meridian times because they are many "light-years" away. A light-year is approximately 6 TRILLION miles away and that is why they falsely seem fixed from our faulty perspective.
Also, in the Bible in Isaiah it says the Lord sits on the SPHERE of the Earth.
Isaiah 40:22 It is he that sitteth upon the circle of the earth, and the inhabitants thereof are as grasshoppers; that stretcheth out the heavens as a curtain, and spreadeth them out as a tent to dwell in:
The word is "circle" (i.e. the word used is for a 2D orbit, not a 3D sphere). From memory, the word for sphere is used earlier in Isaiah, so it's not for lack of words that "circle" was used rather than "sphere".
Peace. I hope you find peace and stop arguing over silly elementary school debates. Be well.
Peace to you also. I trust you have now been enlightened on the scriptures' stance on the Earth's flatness, and you can now conclude your argument with this "silly elementary school debate".