Telco players are accelerating their adoption of cloud native technologies. Indeed, the migration of traditional communications applications to microservice-based architectures will facilitate the development of new network services while providing a high level of granularity. However, cloud native comes with new operational challenges. Indeed, effective network service management requires novel solutions for fine-grained monitoring and tracking of widely distributed cloud native network functions. In this paper, we put forward 5GC-Observer, our proposed framework for the observability of cloud native 5G network services. 5GC-Observer leverages the eBPF technology to track network traffic circulating between 5G network functions and report telemetry data. This demo makes use of our open-source platform, Towards5GS, to implement a real cloud native 5G network on top of Kubernetes. Finally, we develop a statistical technique which leverages the collected telemetry data to detect 5G end-users' Quality of Service degradation, based on real access network information collected from Orange's gNB (gNodeB) located in Paris-Orly airport.