I set somewhere, that all new nodes should be published under 'reports' (domain.com/reports/node) Where can I change this?
There are two possible answers. If you asked exactly what you have asked then you have added a path alias to node under admin/build/path. Or if instead of node/1 you see reports/node/1 then you have pathauto installed and you create a strange pattern reports/node/[nid].
Oh and there is a third one, that you have created a View for all nodes. This question requires clarification -- core only has a listing for promoted nodes not all nodes. Do you have Views installed? Do you have pathauto installed? What happens exactly?