It's ok to be slightly skeptical.
The horizon always rises to the eye level of the observer as altitude is gained, so you never have to look down to see it. If Earth were a ball, no matter how large, as you ascended the horizon would stay fixed and the observer / camera would have to tilt looking down further and further to see it. This does not happen anywhere on earth.
You can observe the new york skyline from New Jersey which is impossible on a ball earth because of "curvature".
Ball earth defies the natural physics of water to find and maintain its level. Rivers would be flowing uphill, for example, the Missisipi River would have travel up about 11 miles. Bridges and buildings plans/schematics don't factor in earth curvature ever. Airplane maintain their altitude without ever dipping constantly which would be necessary on a ball earth.
On a ball Earth, Johannesburg, South Africa to Perth, Australia should be a straight flight over the Indian Ocean with convenient re-fueling possibilities on Mauritus or Madagascar. In actual practice, however, most Johannesburg to Perth flights curiously stop over either in Dubai, Hong Kong or Malaysia all of which make no sense on the ball, but are completely understandable when mapped on a flat Earth.
There's many more proofs. The rotating ball earth model is easy to rip to shreds because you realize there absolutely zero basis for it.
It's reality.
Great circle - Wikipedia, the free encyclopedia