The present paper describes an experimental testbed architecture which incorporates Global Navigation Satellite Sys- tems (GNSS) and 5G cellular systems working together. The testbed was implemented in a real-life environment in the city of Gaia, Portugal. These developments justify addressing the very basic issue of developing a system supported by GNSS and 5G networks, which in real time can provide possibility of positioning with high accuracy over mobile users in urban canyons and other challenging conditions. Using positioning methods such as Single Point Positioning (SPP), Precise Point Positioning (PPP) and Double Difference GNSS, this architecture helps to counter a few of the common problems posed by traditional GNSS systems such as the ionospheric delay, clock biases and multipath. In order to achieve these goals, a crucial element of the testbed is a 5G-based Location Management Function (LMF) which is able to augment GNSS data in real- time to minimize Time-to-First-Fix (TTFF) position estimation and increase geo-location accuracy for challenging environments where GNSS signals may be weakened or obstructed. This system offers a framework capable of dynamically adjusting satellite and atmospheric data, sent via 5G to the mobile platform (which can be a vehicle or other terminal device) in order to geolocate it more accurately. This hybrid environment under which the proposed algorithms will be applied possess a novel nature in terms of current research state-of-the-art, and the objectives of this study deliver the results that positioning when satellite sight is limited will improve when 5G is combined with traditional satellite positioning. It is evident from the results obtained that 5G-assisted GNSS can significantly lower the error vectors, which is a breakthrough in the capabilities of real-time positioning solutions. The next steps will be delivering the system for testing in a moving scenario to confirm its effectiveness in real vehicular and smart city applications. This research adds to the literature by demonstrating the potential combination of GNSS and 5G technologies to address the limitations of stand-alone GNSS systems, which bodes well for the future positioning systems.