In this study, a unique communication strategy is presented. It combines finite block length (FBL) approaches with NOMA and combined one-way and two-way relaying. The paper may be found here. A shared decode-and-forward relay is used as a method so that two source nodes can communicate with one another and then send the information on to their respective destination nodes while adhering to a predetermined restriction on the number of times the channel can be used. Both the from beginning to end block error rate at each node and the system’s net throughput may be expressed in closed-form thanks to the derivation of these formulas. In addition, under conditions of high ratio of transmit signal power to noise (SNR), an asymptotic end-to-end BLER floor is established for all nodes. The outcomes from the simulation are presented in order to validate the conclusions from the analysis and illustrate that the proposed scheme is effective. This paper offers new insights into the performance characteristics of FBL NOMA-based relaying schemes, which helps to a greater knowledge of those schemes.