thanks it did work!

Hi sorry for my late reply, I was waiting for an e-mail:

this is what I have done for now.

the site works with this settings
Your current Parent Theme (Enfold) Version Number is 3.1.3
PHP 5.6
when swithing to PHP 7.0 the site goes blank.

I uploade the child-theme because they had made everything in the parent theme.
via de child-theme I imported the theme settings this looked good, but I still was missing colors settings.
so I changed back to the parent-theme and exported the settings I got a *.txt file.
changed back to the child-theme and imported the settings form the txt file. now the website is back like it should be.

ok but now I need to update the theme.
I uploaded via FTP the new theme over the old one.

refreshed the site.
message:

Er heeft zich een kritische fout voorgedaan op je website.

Lees meer over probleemoplossing in WordPress. (information of the link) https://wordpress.org/support/article/debugging-in-wordpress/

changed the php version to 7.0
still same error message

changed to thisdefine( ‘WP_DEBUG’, true );
define( ‘WP_DEBUG’, false );

and got this message:

Fatal error: Cannot redeclare av_upcoming_events_fallback() (previously declared in /home/plexie1q/public_html/wp-content/themes/enfold/config-templatebuilder/avia-shortcodes/events_upcoming/events_upcoming.php:15) in /home/plexie1q/public_html/wp-content/themes/enfold/config-templatebuilder/avia-shortcodes/events_upcoming.php on line 10