Once you have decided the type of form you need, you'll need to work out which fields to include to collect your data.
This is made easier by the system displaying all the fields that have been created in this List so far so that you can choose to display existing ones in the list on the form, hide existing fields on the form, or add new fields to the form as required.
If you do wish to hide some fields so that they do not display on your form, you can easily toggle these fields ON and OFF by clicking on the eye icon to the left of the field name.
Alternatively, if you do wish to delete a field and all its contents from a list, clicking the Delete symbol on the right of the field and then Saving the changes to the List will remove this field in its entirely from your account.
Therefore, hiding fields is the best way to avoid losing data.
When you're happy with your form, you can start designing the form.