Owncloud to nextcloud

am using owncloud since version 5 and I like it to find an search problems.
Now my owncloud is in version 9.0.4 and I like to follow the new project. Is it easy to upgrade to nextcloud and can I use all the apps am using now?
I am trying to get my speech recognition that owncloud is working according my voice.
There are some commands which are working ( I am using Simon ) but maybe there is a plan
of you doing something else.

owncloud 9.0 and 9 are identical (almost)