Questions from a beginner

Hallo,
today I installed my first longhorn environment and everything seems to work.
As a beginner I ve some questions:

How can I blacklist nodes not to be used by longhorn
2)
Where does longhorn stores its files on the nodes?
3)
Hows can I insert nfs-servers (Centos NFS4 on HP Microserver 8) as targets?
4)
Are there somewhere tutorials for beginners (found some videos) with screenshots etc…
Thanks
Ralf