I actually like this tutorial. Not only does it tell you the steps, but it tells you exactly what you are doing with each command. If something doesn’t work out, you can always revert your last command line because you get a sense of what you are doing.
http://unixetc.co.uk/2016/11/20/simple-nextcloud-installation-on-raspberry-pi/
If you do decide to move the directory to make it safer, on raspbian at least. Vi (text editor) will not let you changethe permissions. Leafpad will.
So instead of command line :
sudo vi config.php
sudo leafpad config.php
Also, make sure to forward ports 443 and 80 to your raspberry pi, otherwise you cannot access it online. And what is a cloud without accessing it outside of network?
To forward ports first find your IP address here:
https://www.iplocation.net/find-ip-address
Then type it on your browser and that will take you to your Router portal, where you can forward ports. If you have trouble forwarding ports look up your router brand and type and forwarding ports on google - that’ll tell you how to do it specifically with your router. Otherwise comment below and we can try and help.