Dear Errrrrrrrrrik,
Good day! Thank you for posting your query in our community. We are happy to help you.
Based on your description, you want to export Forms responses to Excel and save them to SharePoint.
If your SharePoint site is connected with a group, then you could create the Excel file and form via the Forms for Excel option under the "+ New" button in the library, a new form and a related Excel workbook will be created via this option. So all the responses to the form will be saved to the Excel workbook automatically. However, you need to manually add the questions in the Forms instead of copying from the old form.
If you still have a concern about it, please feel free to post back.
Sincerely,
Jazlyn | Microsoft Community Moderator