Hey there Globuff,
Thank you for posting in the Apple Support Communities. I understand you are unable to locate Keychain Access, and it appears the folder is missing from your user Library.
It sounds like you'll need to reinstall macOS. I've shared the steps to do so below.
* Reinstall macOS
"When you need to reinstall macOS on your Mac, you can install it from Apple using the internet or you can install it from the recovery partition included on the hard drive or flash storage of every Mac. Both ways of reinstalling keep your files and user settings intact.
Important: You must be connected to the internet to reinstall macOS."
Have a good one!