DESY (Deutsches Elektronen Synchrotron) is currently expanding the PETRA III storage ring X-ray radiation source to a high-resolution 3D X-ray microscope providing all length scales from the atom to millimeters. This PETRA IV project involves an optimization of the girder magnet assemblies to reduce the impact of ambient vibrations on the particle beam. For this purpose, an innovative and biologically inspired girder structure has been developed. Beforehand, a large parametric study analyzed the impact of different loading and boundary conditions on the eigenfrequencies of a magnet-girder assembly. Subsequently, the girder design process was generated, which combined topology optimizations with biologically inspired structures (e.g., complex Voronoi combs, hierarchical structures, and smooth connections) and cross section optimizations using genetic algorithms to obtain a girder magnet assembly with high eigenfrequencies, a high stiffness, and reduced weight. The girder was successfully manufactured from gray cast iron and first vibration experiments have been conducted to validate the simulations.