Here are links to some of the utilities we like. Call us if you need help with them.
Auslogics Disk Defrag
After you clean up the temp files and remove old downloads. Then run this utility to organize the files on your hard drive for faster retrieval.
Be careful during installation, do not allow additional software to be installed.
When selecting to defrrag, select "Optimize".
We know you are used to paying for anything Mac, but here are two free utilities that you will love. The first one is similar to "Clean my Mac". The other is an antivirus. Yes, Mac's do get viruses.