@louisphilibadc 

Please downgrade your php version as Magenot 2.3 supports below shared PHP version:

https://devdocs.magento.com/guides/v2.3/install-gde/prereq/prereq-overview.html

After that just run below commands:

php bin/magento setup:upgrade
php bin/magento setup:di:compile
php bin/magento setup:static-content:deploy -f
php bin/magento c:f
chmod -R 0777 var/ pub/ generated/