Hi!
Thank you for your question. The closing balance in 2021 have to be the same as the opening balance in 2022, so you can't change just the numbers but have to actually correct it via manual bookkeeping vouchers. When you say that it gives negative values, do you mean that some accounts show up as minus that shouldn't have a minus in front of it? Then you need to look over the bookkeeping in 2021 to see if something has been bookkept wrong so you can decide how you can correct it. According to the "god redovisningssed", corrections from closed years should be handled in the next open year usually, which you can read about here. Depending on how big the fault is you might have to correct the tax report for that year again but do the actual correcting in the bookkeeping in 2022.
I recommend that you get help from an accountant if you can't find whats wrong in with the negative values or if you don't know how to correct the inventory.
Have a nice day!
Josefine