No need to delete! Go to forms, click the wheel icon on the form you want to hide and click unpublish
Hiding pop up from your website
Go to marketing > tools. The window 'popups' contains all popups. You can make different popups and don't have to delete them. When a popup is published it will have a blue circle. If grey, it's unpublished! If you click the "wheel icon" you can publish or unpublish the popups you prefer