Service DTOs should not have any prefixes/suffixes: User.
DB entities should have Entity suffix: UserEntity.
Properties on classes that are exposed outside the service (i.e. Events and their respective Models in Service.Contracts) should use camelCase when serialized, meaning they need to be annotated with a JsonProperty attribute.
Split code into namespaces by domain, i.e. User namespace should contain code dealing with user stuff, i.e. repositories, models, entities, services and etc. Don't create namespaces, like Repositories, Services and etc.