Please let me know what will happen if i cancel my subscription after one or two months? Will i get my extended Gbs that i paid for? Or will it take me back to 5gb

When you cancel, you will go back the 5GB of free storage. You are not buying permanent storage. You are renting a fixed amount of space for a monthly charge.

Think of it like renting a storage locker. You pay a monthly free for a fixed amount of space and when you cancel your lease, you lose the storage space. You don’t get to keep the space.