If your database is too large, you might want to update your mailwizz application from command line rather than the web interface.
In order to do this, follow the upgrade steps as described here but once you reach the update screen, do not press the Submit button in that screen to start the update process from the web interface, instead, read the first paragraph of the page carefully.
That paragraph will give you proper instructions as what command to run from command line to start the update.
The command you have to run looks like:
/usr/bin/php -q /var/www/html/apps/console/console.php update
In your case, most likely instead of /var/www/html/ you’ll have some other path.