5000 item limit- worked before and after changes not working anymore

[D-Rum_123]

Hi,

I recently exported my sharepoint list to excel so I could update the details of one column. 

I chose to do it this way as it's quicker in excel to populate one column that had many empty cells with a default value.

Now I re-imported the spreadsheet back into the same list and now I get these errors (note the number of rows did not change):

When I try and view the list I see this:

When I changed back to the classic view I see this:

Lastly, under settings I see this:

Thank you and please help me get back to functionality.

Regards, 

Daniel

[#2]

Hi, I think I know what I did wrong. I assumed that if I did the "append to" query in Access whereby I push the rows from the updated version of the excel table to the sharepoint list that the item codes which are unique fields would cause those existing records in the SP list to update. Instead it created those lines as new lines increasing the total number of records. I ran this query numerous times as i kept getting errors on the query but it appears that those queries were at least partially successful. The original number of items was 2540 and now it's 10x that amount. Is there a way to retrace my steps and restore my list to an earlier version before all these new items were added?