Hi Jeroen,
For deleting entries you can have a look at https://docs.gravityforms.com/delete-entry-data-after-submission/.
You need to realize that we do not always have the payment status directly after the form is submitted. So deleting entries if the payment is not successful can not happen right away. Sometimes it can take some time before the payment is processed and we receive the confirmation of payment. So if you do other stuff with the entries you should probably make sure that you only trigger the other stuff if the entry has the desired payment status. For front end loops you could also make sure that you only show the entry if the payment status is what you want.
Please have a look at https://docs.gravityforms.com/entry-object/ and then the payment_status field. Our plugin also has a hook that might be useful for you if you want to trigger processes directly after the payment is complete.
do_action( ‘gform_mollie_payment_retreived’, $entry, $payment );
I hope you understand that you are asking something that goes beyond the free support we can give on on our plugin and we can not work out a complete solution for your use case.
