I’m trying to log into my Apple ID but another one is signed in and I dont have password

The person who signed in needs to log out of iCloud or go to https://www.icloud.com/find/ and erase the device, then remove it from their account. If they won't do that, the device is useless.

Turn off Activation Lock - Apple Support.   *

If you are the original owner, contact Apple. Apple can remove the ID  if provided the required paperwork to include the original purchase receipt with the serial number on it. 

Request additional support for unlocking your device.    -

You used to be able to take the device, the original purchase receipt with the serial number, and a photo ID to the nearest Apple Store (if it has reopened) and have them remove the ID. This may have changed, so call the store before going to make sure they can help.

Genius Bar Reservation and Apple Support Options - Apple.   -

Did you buy the iPad brand new or did you buy it serving hands from someone rose? Do you know the person whose Apple ID it’s asking you to sign into?