Your form template was made a while ago and you've already used it several times on your forms online. Here’s what you can do to change your form templates while making sure that this updates the associated forms:
Any change/edit/deletion/addition to a field in your template will automatically update the associated forms.
Click on the green button at the bottom of your template: this will let you perform any update to your template manually.
You will arrive at this selection window:
Notification by email
You can change the email addresses of the people to alert internally.
The thank-you message
You can change the thank-you message that appears follow a form submission, or even the chosen redirection URL.
You can also change the consent text as well as the consent fields annotated to the bottom of your forms.
Note: The green button does not allow you to update the thank-you message send to the lead follow the form submission. The reason is because this button would be a “dangerous” shortcut and would risk removing all the right document-download links connected to your content.