A fundamental difficulty in dense device deployment settings and typical 5G use cases such as massive machine-type communication (mMTC) is establishing seamless connectivity with minimal interference. In this work, we address this challenge in a dense cellular network. For enhanced connectivity, we deploy a decode-and-forward (DF) unmanned-aerial-vehicle (UAV) relay which serves over a region $R_{c}$ of the network, and for overall interference management, we propose a novel scheme for resource block (RB) allocation among the base stations (BSs) and the UAV. The simulation results for our scheme show promising improvement in the number of user equipments (UEs) achieving their desired rates.