Use Simulink Profiler to determine which part of the model is consuming the most execution time: https://www.mathworks.com/help/simulink/slref/simulinkprofiler.html?searchHighlight=simulink%20profiler&s_tid=srchtitle_support_results_1_simulink%20profiler
Adjusting solver settings can often improve performance. The Solver Profiler can help with this: https://www.mathworks.com/help/simulink/slref/solverprofiler.html
Accelerator and Rapid Accelerator modes can also help.
Thanks.
Mark.