If a main windows 10 account has malware will a guest account be safe

Question

If the admin account has a keylogger and I make a guest account , will the guest account be safe or will that too be logged and infected

Answer 1

No account will be safe. Malware affects the system as it installs itself in the root directory. So all users on that machine are affected.
To get more technical, Malware piggy-backs on other software (usually) and installs itself to run as a service on that machine.
This is sometimes the reason why Malware can also easily re-install itself.

Answer 2

If any admin account has been compromised on your system, (Windows, Linux, Mac, *BSD), then the entire system is pretty much compromised, unless the malware is incredibly poorly written. Admin accounts tend to have full access to all of the system's resources and can make any changes they want. This is why you should always be using a non-administrative account for day to day usage. If you're only using a regular account, the amount of damage is typically limited to just your account and anything you've been granted access to. Mind you, some malware is capable of gaining administrative privileges on a regular account; but those are due to flaws in the OS, or perhaps a service running in the background.