I have issue in firebase firestore snapshot with limit and pagination

I am working with Firestore right now and have a little bit of a problem with pagination. Basically, I have a collection (assume 10 items) where each item has some data and a timestamp. and First 10 items get with snapshot orderBy(createdAt ,desc) after that I take one variable as a last record and i used it in another query as a startAfter clouse but when I add new record then first item is removed if we have one array in that we have 1 to 50 items then on the first time i get 10 item with snapshot like 1 to 10 and If I add new item then 1 is remove and new item is pushed in array and if I clicked on load more button then in the list i saw 1 is removed how can I solve this problem? EX. In firebase collection Array = [2,3,4,1,8,7,6,9,5,10,13,12,14,11,16,17,18,20,15,19] first snapshot with order by createdAt desc and limit 5 I get and I also use docChange() method in snapshot 16 17 18 19 20 after i clciked on Load More this is get() method same as above limit ,orderBy and startAfter then I get 11 12 13 . . . 20 if i add 21 then I get 11 12 13 14 15 17 18 19 20 21 after reload I get it back in perfact order My Tasks are: 1.Delete items from array with real time upsdate 2.Edit Items with real time upsdate 3.At the first time I only want to use Snapshot with limit 10 4.After than other record get with simple firestore get() query