I've already done extensive research on this topic and can rapidly review all possible issues (including everything done at the Apple Genius Bar in Apple Stores).
Including:
- Review memory and CPU usage for anomalous activities
- Check drive capacity and usage
- Check hardware type, status, and condition
- Reset various system settings that can cause slow downs
- If needed, can assist in complete erase-and-reinstall of system
S'il es necessaire, je parle français aussi :-)