It's proven fact from the experiments that scientists have done. For example, have you ever watched the lunar eclipse? You can see the shadow of the earth covering the moon every time the lunar eclipse occurs. And, the shadow shows round in shape every time. This is a clear example. If you still have doubts, read https://www.space.com/38931-kids-can-prove-earth-round.html and https://www.popsci.com/10-ways-you-can-prove-earth-is-round#page-10

I hope you are now clear with your doubt. Still you have doubts, contact the research writers who can provide you comprehensible data on your questions.