Changing your password will not stop hackers. There are benefits to occasionally changing your password like protecting against other kinds of cyber threats. However, there any many ways for hackers to gain access to your account.
Password generators are safe. The main concern is how your new password is stored. Password generators generally do not store your passwords but simply create them. Avoid concerns by using a password generator independent of the site for which the password is created.
No Password Manager is 100% safe. Google’s password manager is built into the browser which can raise its own vulnerabilities. However, their convenience and encryption offer an alternative to less secure password saving methods.