cleaning my system

You paid Apple good money to build into macOS elegant and automated self-maintenance routines. They run on a schedule, usually in the wee hours of the morning local time when most people are not using their computers.

Macs, cat-like, clean themselves.

If the computer is sleeping, no problem. The routines wake it up, quickly do their thing, then put it back to sleep when done. If the computer is off at the appointed time, the routines run during the next idle time after startup.

They do all required maintenance, including defragging with no need for user action. An occasional restart takes case of everything else.

This elegance has been part of macOS for almost a quarter-century. So what does that make the third-party software that claim to do the same thing? Hmmm. I can think of a short word that starts with "s" and ends with "m."

Worse, third party "cleaners" interfere with what Apple have provide and can actually slow the computer. Alleged "cleaning" apps have also been know to delete important system files, leaving the computer a crippled mess.

Let your Mac be a Mac.

If you are talking about cleaning the computer's system software, there is little to be done. What is your issue? Some things you can do are noted below. They are “maintenance” steps which are often ignored.

·      It is important to occasionally restart a Mac. Ideally, once a week or more often. This does some system cleaning.

·      Regularly clearing the history of your browsers can help as all the data is stored in RAM. Clearing frees up RAM for system use.

·      If your computer is set to startup with too many apps that will slow down the startup process.

·      Some programs use a lot of RAM. (Like many Adobe apps and the Chrome browser.) When using them, close any other apps not being used.

·      Doing a restart in the safe mode can clear a number of problems. This is done by holding down the Shift key at start up. This process can take up to ten minutes while the computer is doing its maintenance and cleans the cache. You may then restart normally.

·      It is also a good idea to run the Disk Utility app. If it reports some issues, then rerun it repeatedly as needed until the final report is ok.

·      Last, and most important, you should remove any and all maintenance and antivirus programs. They will cause problems and will significantly slow your computer.

·      It is also very useful to download and install the free app EtreCheck. Be sure to enable full disk accessand run it. Save the report. You can post the results here at the bottom under “Additional text”. It will tell us exactly what you have installed which might be problematic. Then we can offer some specific suggestions.

I hope these suggestions are helpful.

Is it dirty?

If you are asking about cleaning your Mac, read How to clean your Apple products - Apple Support