Need Help! Transferring Data from one spreadsheet to another at speed???

you ebay list is a pivot table source - do you have the database that drives that ?
update - means what
replace the value from nevis and put it into ebay

a lookup would do that
using an indirect to a cell to reference the worksheet - so that when you add the new data as a sheet and rename its not changed to reference
OR
you could copy over the data each time you get an new list

you have negative stock amounts in the Nevis Stock file

Can you answer the other questions - the ebay sheet is your spreadsheet - and it looks like a pivot table - so how is this sourced ???

nevis has negative numbers - do you want those in your "stock list" ebay sheet

as i said use a lookup and just copy the data in
heres a sample sheet

On the spreadheet - goto to the stock list sheet
delete the data in stock list
Select A2,B2,C2
then use

Control + Shift + Enter keys
that takes you to the bottom of the data and then right click and clear
now goto the new nevis stock sheet
and select A2,B2,C2
Control + Shift + Enter keys
now right click copy

go back to the ebay spreadsheet - stocklist sheet and
click on A2
right click paste
now all the values are entered into the spreadsheet and updated on the ebay sheet

try that - i can probably improve on it - if its close to what you want

Cell M1 is used as an indirect to stop ref errors on the ebay sheet - so must not be deleted - we can change this as well

the ebay upload is not sourced from anywhere. I created the template/table and the information on it is relative to current ebay listings that I have on ebay now. I can then upload this file via their 'file exchange' system and their system can recognise it and alter my listings.
The ebay upload template can't be altered in any way because eBay will no longer be able to read it.

And no, I can't have any minus numbers. I also noticed there is another issue as well... The stock update that they send me has some errors eg, a duplication of an item and one will say it has 10 stock, and the duplication will say it has -8. The number that isn't the minus number is the correct one.

Using control + F and searching for each item individually to change the stock has proven to be too time consuming

Hi,

Your type of problem is exactly why Microsoft built a new tool into Excel called Power Query, which is now called "Get & Transform" in Excel 2016. You will need to upgrade your version of Excel to get this newer tool in Excel. But when you do see the link below to see how you would do your daily task.

https://www.powerquery.training/portfolio/merge-tables/

unless someone knows how I can do it through my current version.

did theprocess I posted not work at all for you
we do need to remove the duplicates and modify for negative numbers - otherwise - takes a few minutes to update the entire spreadsheet with the new values