i am confuse

Hi, i am asking a kind of stupid or nonsense question.
Is world really in a ball shape?
and it is said if you are in NY or any where in the world, and if you keep going straight one day you will be back, at your base where start walking.
Ok, if the word is in a ball shape or round.
so why people dont fall from the ball,
for example if you put a coin on a top of the basketball, and ofcorse you cannot put a coin on the bottome of the ball............on the other hand, maybe less say on the top of the ball (earth) there is USA, left, Russia, right india, and on the bottom china, located.
so how come on that ball Russia, China and India will stay, USA will stay because it's on the top just like a coin on a basketball.
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i am very confused about the ball but i know you are not confuse because you have the answer for my problem.
please take it easy
and thank you
BYE