No the earth is not flat. Have you ever flown on a commercial airplane flight? I always wanted the window seat so I could look out. And those windows (they're flat, no fishbowl effect on the ground) show you a sort of spherical earth.
Then watch the video from the SpaceX launches as it goes up to 100 miles or so, and the earth becomes more obviously spherical.
And on the ground why is there a horizon?
If the earth were flat, wouldn't there be an edge? Wouldn't we have people exploriing the other side, or drill thru to the other side?
And why would it be flat? How would a flat surface be formed by natural processes in space? A sphere is formed because stuff gathers around the center, pulled in by gravity. A flat thing? How would that even occur?
You're right to question things, but I hope you'll also consider the scientific proofs above. If you're still suspecting flat earth, please try to refute them. People much smarter than me could not refute them.