Briefly, under your circumstances, to remove the activation lock you will need to have the Apple ID password used by the person possessing the device prior to erasing it, and, we can't help you with that. And, Apple support will not help unless there are extenuating circumstances (e.g., you have the receipt for your purchase of the device with its serial number on it or a court order instructing Apple to assist in the provision of access to a decedent’s information from the deceased person's accounts). To deal with the possibility you have an extenuating circumstance, use these support options:
Get a call from Apple support to help solve your problem using this link https://getsupport.apple.com/?caller=kbase&PGF=PGF63005&category_id=SC0245&symptom_id=23362
Apple ID Support https://support.apple.com/apple-id
Apple ID account security for country-specific and
region-specific help https://support.apple.com/en-us/HT204169
Get Support: We’re here to help https://getsupport.apple.com/. Go
through the options to find the best support option.