I would normally suggest to merge the SPR’s and the remaining of the structure in CAD, but in your case the SPR’s and the rest of the structure consist of different materials, so that would not work.
With that being said, try to optimize the mesh settings - I noticed that most of your meshes have a large value for the global fineness:
The global fineness, as the name suggests, is applied to the entire structure. This will generate extra cells in the regions of interest, and also in the regions which don’t require a fine discretization.
Therefore, I’d recommend reducing the fineness back to default (5) and applying local element size refinements to the regions of interest (e.g. the bolts).