Hi,
How are you going one with this one?

Basically, I would check is PHP working. Create a file test.php under your html root (if you use default settings it is /var/www/html).

nano /var/www/html/test.php

Write following content in it:

<?php
phpinfp();
?>

Save it and close editor. Go to http://droplet-ip-or-domain/test.php and you should see PHP info page. If this is not the case write here and we will try to find out what’s the problem.

If you see info page, make sure you have required PHP7 plug-ins.
You can try installing them and you will see is something missing:

sudo apt-get install php7.0-mysql php7.0-curl php7.0-gd php7.0-mbstring php7.0-mcrypt php7.0-xml php7.0-xmlrpc

After install is complete restart Apache

sudo systemctl restart apache2

Try to access your WP site and hope for best :)