1) acf_form_head() must be output before any html, so before get_header() is called and not just before the form. Is this the case.
2) acf_form() must be called inside or the <form></form> tags of the existing form. Is this what you’ve done?
3) I do not understand why you are attempting to update the fields manually in the second part of your code since ACF will do this for you if you’ve set up the form correctly.
