A safe password today should
- be at least 12 characters long, but the longer the better,
- be as complex as possible, e.g. by including numbers, capital characters and special characters, and
- only be used for one service.
There are a lot of services that require a password, and computers will always be better to remember a long and complex password than humans. Therefore, a password management software is highly recommended. Some free and open source password management systems are Bitwarden, Clipperz, KeePass, LessPass, Padlock or Passbolt.