Is Clean My Mac" a safe program to use?

No, it is not. It's been known to clean over aggressively deleting important system files.

No Anti-Virus software or so-called “cleaning” apps are needed or recommended for Mac OS. They can conflict with Mac's own built-in security. At best they will slow your Mac by using unnecessary resources and at worst will bork your entire system. Your Mac has all the built-in protection you need.

https://www.apple.com/macos/security/

What previous post said. Clean My Mac and other "third party" anti-virus apps are all "GARBAGE!" Do not believe what you see in YouTube, or other "social media," about Mac app cleaners.

A total garbage app, as are all other "cleaning" apps and antivirus apps for Mac OS.

Generally considered as one of the last things you want on a Mac.