will clean my mac hurt me computer 2020 imac big sur

To expand upon that a little bit further: Tthere is no reason to ever install or run any 3rd party "cleaning", "optimizing", "speed-up", anti-virus, VPN or security apps on your Mac.  This user tip describes what you need to know and do in order to protect your Mac: Effective defenses against malware and other threats - Apple Community.  

There are no known viruses, i.e. self propagating, for Macs.  There are, however, adware and malware which require the user to install although unwittingly most of the time thru sneaky links, etc.   

Anti Virus developers try to group all types as viruses into their ad campaigns of fear.  They do a poor job of the detecting and isolating the adware and malware.  Since there are no viruses these apps use up a lot of system resources searching for what is non-existent and adversely affect system and app performance.

There is one app, Malwarebytes, which was developed by a long time contributor to these forums and a highly respected member of the computer security community, that is desshoigned solely to seek out adware and known malware and remove it.  The free version is more than adequate for most users.  

No. Here's my explanation:

You may have heard of software such as CleanMyMac that claims to remove "junk" from your mac. The problem with this is that the "unneeded files" and "junk" it finds are sometimes essential to the proper functioning of an app or even macOS itself. Delete the wrong file from your mac, and you might have to reinstall macOS or the applications you use. Do you really want to trust an app to tell you what is safe to delete and what isn't? No, it probably won't do anything too bad or give you a "virus," but the services it offers will do almost nothing to speed up your computer or free up space. It is not very helpful at its best, and can cause serious damage at its worst.

There is really no such thing as a "dirty" mac.

https://support.apple.com/en-us/HT206996

I would not install CleanMyMac X on any Mac.

We certainly don't recommend it around here, some echoing the literary quote: "This is not a novel to be tossed aside lightly. It should be thrown with great force"

You're welcome.