Invoices and Inventory Items

Yes

That’s correct

From what you have described above you have done a lot of activity perhaps without checking each step so can I suggest - delete your imported bank account transactions and delete your purchase invoices transactions - this should leave you with your Suppliers and Inventory data with out any associated values.

Enter one Purchase Invoice with a few Inventory items - after creating that invoice check that the related inventory have updated correctly, now do more Purchase Invoices etc, Once you have that working ok then do the imported bank statement transactions and check the results each time.