Is this possible?

[SallyVating]

Someone is claiming to be able to see all my messages, WhatsApp, messenger, text etc and also see my locations and track where I've been.

Phone is a Samsung s8 and I've set eyeball recognition and a password. Checked all apps and disabled location sharing etc.
I'm thinking that they're bullshittimg but a bit spooked nonetheless. I've also checked for any apps I don't recognise but didn't find anything.

It is possible for them to have installed an app to send them all that, and then have hidden it from you. This sort of thing could also have been done if they have the password to your Google email that you use with the phone.

Only way around it is to change your phone, set up a new Gmail account, and reset all your account passwords and set up two factor authentication (2fa) on all accounts that have it.

Step 1, turn off your current phone
Step 2, set up a new email account and change all your passwords on a new device that you use just to change the passwords, set the new email as the reset address for all the accounts.
Step 3, buy a new phone, with a new sim card, use your new Gmail account with it, sign in to everything and enable 2fa on all your accounts.