Hi OlgaS1.
Importing information into your QuickBooks company file is a great way to update your lists quickly. I'd be happy to point you in the right direction to get this resolved.
When you import information into your company file to adjust items and the price and cost it will have an affect on your books. In order to fix this I recommend reaching out to your accountant as they are trained in how to do this. If you don't have an accountant no worries, we can help. You can go to our find an accountant page to find one in your area that can help.
If you have any questions let us know and we'd be happy to help.