If you can indeed sign in and the only issues are apps that need updating, delete those apps and download them with your ID. They must be updated using the account that got them in the first place.
If it ends up there are other issues with the previous owner's ID, you need to ask Apple to give you access. For information about how to request access to a deceased family member's Apple account data, and possibly their equipment, read this support article --> How to request access to a deceased family member's Apple account - Apple Support The device "belongs" to the person's who ID is signed into it.
Alternatively, if you have the receipt for its purchase, Apple can completely reset a device if a person can provide sufficient evidence of valid ownership. Do this online at: Activation Lock support request - https://al-support.apple.com/#/additional-support Apple says, "Proof of ownership documentation is required," but does not detail what currently constitutes proof. Prior to this new online service Apple typically required the original receipt issued by Apple or an Apple Authorized Reseller and documented provenance (so typically it would be the original owner who does this, or a descendant with legal proof of ownership). This will give you access to the device but won't restore access to the account used to lock it. There is nothing that can be done to expedite an Activation Lock request.
Apple recommends you "Keep your receipt after you buy an Apple device" --> Keep your receipt after you buy an Apple device - Apple Support
