Setting up nextcloud on a raspberry pi 3

Hi Everyone,
I would consider myself new to linux and nextcloud, although I have setup owncloud 8 on a raspberry already.

This is what I want to achieve:
I want to setup the raspberry with nextcloud in that way to use is as cloud storage/file collab space (at least i want to try most of the available apps if they would make sense to use)
I would like to administer approx. 20 people who all would have individual and shared space. (for that i think a mysql database would be best as we also want to use the desktop client)
As I only have a 64gb sd card installed I would like the files being saved on an external hard drive.

The cloud should be accessible via internet using one of the free domains like offered by dyndns.
As the IP address is distributed dynamic by my provider a dynamic dns updater is necessary.

I have found several (different) guides and as said i already was able to set it up with owncloud 8 with one of these.

Could someone help me in setting up that pi with nextcloud with the features I would like to use?

Thanks a lot in advance!

Well you can have a look at the following two topics:

Other than that Nextcloud is not that different from ownCloud atm, so you can just update your ownCloud raspberry to Nextcloud: