To do optimization, you need a model that solves in a short time. I expect your model is all solid elements, and takes a long time to solve. If you change your model to be all shell elements, it will solve in a much shorter time. I recommend you convert your solid bodies into Midsurface sheet bodies, and create a shell element model of your optimization. Please show your geometry.
If you can't use a shell model for some reason, then you must make the mesh as efficient as possible. If your mesh is Tet elements, you can reduce the number of nodes by about half if you replace that with Hex elements. Please show your mesh.
Another idea is if you have turned on Large Deflection, but the deflections are small, turn off Large Deflection and the solver will do fewer iterations to get to the solution.
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