Thank you for your reply. Actually, I understood just now where the problem lies and both issues were related.
I created 4 columns in Sharepoint called "Created", "Created By", "Modified" and "Modified By". I thought that both tests did not appear on Sharepoint, but they appeared at the bottom of the list because none of these 4 columns were filled in. I have attached a picture that shows the blanks.
I don't know what to add in the App for these columns to be filled.