You could adopt practically anything. You could take a child, that is not yours by birth, and make them part of your family, by what we call today ‘Adoption’. You could adopt a child into your family, you could adopt new thoughts, actions, habits, new role models, etc. How does this relate to Paul’s thought? Well he is telling us that we could change our hearts, from worshiping one idle to another. Let’s say that someone’s father dies and then mother dies not too long afterwards. The orphan cold either live on the street, or live in an orphanage, or live with one of their parent’s siblings, or live with an older sib that is an adult or and married. If the orphan is accepted, then that orphan is not an orphan anymore. The child is then adopted, because she/he is adopted into an family and the child adopts to their new guardians as new protectors, careers, and providers, and maybe even as their new parents.
Inheritance is a gift from the deceased to the living. A person does not need to die to had what is theirs to someone else. When a king dies either, the kingdom goes to the new king that is the voted choice of the people, or to one or all of his descendants, or by a chosen person of the king. Something could happen and that person still live, but hand over their whatever to someone long before they died. When you are born, you inherit something from each parent and maybe something from each grand-parent. How does this relate to Paul’s thought? Well when we get resurrected, we are going to inherit many things from God our Father, like maybe a/one or a few mansion(s) (not man-made here on earth), yet God the Father still does exist, and will exist forever and ever. And yet we might/most-likely-will inherit many things from God the Father.