So the nodes are centralised; how do I know that my data is safe?

Yes, there is some form of centralisation that comes with the model which the nodes are built upon, however, this lowers the hurdle to entry for the end-user by not having the set up expensive hardware and having technical know-how to be able to run the node. Adding to that, the multi-layer protocol on which Nerian runs makes it impossible for the team to view or access any user personal data stored on these nodes.