Hi @saavedrajj
The gallery field expects the value to be saved as an array of attachment ID’s.
What you will need to do is loop through your images, and use a WP function (check google / WP codex) to insert the attachment. I have done this before, but can’t rember the function name. That function will return you an attachment ID which you can use to then later save an array via the update_field function.
Hope that helps.
Thanks
E
