You can download product information to your computer. First, go to the "Products" tab and select "Export to CSV". If you want to include wholesale prices in the product download, first select the product catalog opened for you by the reseller, and then select "Export to CSV".
If you open a CSV file in Excel, Excel can interpret values in euros as dates. This can be avoided by first opening Excel, then selecting the "Data" tab from Excel, and then opening the CSV file via the "From Text / CSV" function (this may be slightly different in different versions of Excel).
You can use downloaded file to update prices and upload it back to Glue.