How can I manage CSV layout differences for product uploads?

Hello!

I am starting a new store and am looking at uploading products by CSV, however my supplier’s live CSV is in a different layout to what shopify accept and often has products added and removed. So it will be almost impossible to keep up to date with stock movements as it wouldn’t be a copy and paste job due to the products moving on different lines once new ones are added.

Can anyone recommend or advise what I could do here please?

I hope this makes sense