Intercept specific Gravity Forms form submission and process it only if it's the one we want

gravity-forms-process-form-if-matches-acf-option.php

<?php
/**
 * Intercept form submission and process it
 */
function gf_intercept_form_submission( $data, $form ) {
	if ( (int) $form['id'] !== (int) get_field( 'submit_project_gf_form_id', 'option' ) ) {
		return;
	}

	// Do something with $data
}
add_action( 'gform_after_submission', 'gf_intercept_form_submission', 10, 2 );

See https://gist.github.com/psaikali/2b29e6e83f50718625af27c2958c828f for the first part