In quantum many-body physics, Quantum Field Theory (QFT) provides powerful tools to describe collective particle behavior. This framework employs three crucial theoretical tools: Green's functions for characterizing particle propagation and response to perturbations, Feynman diagrams for organizing perturbative expansions of quantum processes, and renormalization for improving the convergence of diagrammatic series. A key challenge in QFT is the efficient representation of finite-temperature Green's functions, particularly at low temperatures. We develop a universal framework linking the effective degrees of freedom in these functions to the rank of Lehmann eigenspace, explaining the observed compressibility in Discrete Lehmann representation (DLR). To address numerical instability of DLR in self-consistent solvers, we introduce the symmetrized discrete Lehmann representation (SDLR), which incorporates physical symmetries while maintaining computational efficiency. Applying SDLR, we study phonon-mediated superconductivity in the uniform electron gas (UEG), focusing on the Coulomb interaction effects. Our analysis reveals that the conventional Coulomb pseudopotential $\mu^*$ stems from two distinct effects: modifications to the Fermi Liquid factor and alterations of effective couplings. To extend our first-principle approach to lower electron densities and real materials, vertex corrections in higher-order Feynman diagrams must be systematically evaluated. This presents a significant challenge due to the factorial growth in diagram numbers at higher orders. We address this by transforming Feynman diagrams into computational graphs, enabling efficient computation reuse across shared sub-diagrams. Furthermore, we incorporate Taylor-mode automatic differentiation to streamline the computationally intensive diagrammatic re-expansion process. This approach reduces the computational complexity from exponential to sub-exponential scale relative to the differential order, as demonstrated through calculations of the UEG effective mass ratio. This research advances computational approaches within QFT by combining theoretical physics with advanced computational methods, establishing a foundation for future interdisciplinary studies of quantum many-body systems.