is it possible that a buyer can reduce the price after order placement? If a buyer asks for changes and says that your work in not too much so you should charge me less. Then what will be the procedure to reduce the amount.
There is no procedure for that. Please refer your buyer to read fiver TOS and tell them that fiverr doesn’t have feature to reduce order amount.
But, I think there should be an option so mutual cancellation and resolutions will be nicer to resolve.
You do have an option to cancel a complete order but you wouldn’t be paid for your work at all.