Package apache2 has no installation candidate
Package apache2 is not available, but is referred to by another package. This may mean that the package is missing, has been obsoleted, or is only available from another source E Package apache2 has no installation candidate

sudo apt-get update && sudo apt-get upgrade
Ensuite installer Apache2
sudo apt-get install apache2
sudo apt install php libapache2-mod-php
sudo apt-get install php-curl