Is there a way that I can download products and services into excell and then change the cost and sales prices and then upload it again?

It's a great day to have you here, @jacobs-henk,

Glad to hear that you want to explore the features in our program. Allow me to share some tips on how you can update your products and services through exporting and importing them.

To get started, follow the steps below:

1. From the Sales menu, click the Products and Services tab. 
2. Tap the Export icon then click the .XLS file at the bottom.
   
3. Make the necessary changes in the Excel file. Make sure to enable editing so you can save the changes.
4. Once done, save the file for the import process. 

When you are ready to import the changes, follow the steps below:

1. In the Products and Services page, click the drop-down beside New.
2. Press Import then the Browse button to find the saved Excel file.
   
3. Click Next then proceed to mapping the data. Click Next when done.
4. Double-check the information then scroll down to the bottom of the page.
5. Mark the check box for Overwrite all values for each product or service that you import with the identical name. (This can’t be undone.) box. 
   
6. Hit Import.

These articles highlights the entire process of updating or adding products and service in QuickBooks:

• Import products and services from Excel
• Move your lists to QuickBooks Online

If you need additional help, just message me again so I can help you further. Have a nice day!