Want the new updates to append the data in the google sheet instead of and changing them(pls read the full question , also my English may not be that good so sorry in advance)

once the user updates the data is there a way to store it …let say i have this app about inventory of a shop with 4 types of products 100 each type and everyday some product is being sold at the end of the week i want to know which day which item (s) and what quantity of it was sold …every time i update the item the previous item gets updated …say Monday i updated product A from 100 to 90 ( 10 items sold ) so one till Saturday every day i sell 10 items of product A on Sunday i will have 30 items left and will have 30 in the sheet but i wont know how many items i sold every day is it possible to have the app store every update in the same or a different sheet.

You should review the inventory management sample apps.