Are you talking about a new Google account @HyeonJ? If so go to Settings > Cloud and accounts > Accounts > Add account > Google and you can setup a new Google account in there. Although I'm not sure if the new account will replace the old one or you'll have 2 accounts to switch between.
I'm using the s8 and after having a look around it I cannot see a guest mode or different user profile option.
You can use Secure Folder to lock away sensitive information if your thinking of letting someone else use your phone.
Current Phone ~
Samsung Note 20 Ultra 5G SM-9820 _256Gb SnapDragon 865+
Samsung One Ui 2.5/ Android 10.