LOL! If you take Genesis 5:5 literally, you would have to conclude that "one day" = "one year!" However, I have an even better scripture for you to look at:
Deuteronomy 31:
16 And the Lord said unto Moses, Behold, thou shalt sleep with thy fathers; and this people will rise up, and go a whoring after the gods of the strangers of the land, whither they go to be among them, and will forsake me, and break my covenant which I have made with them.
17 Then my anger shall be kindled against them in that day, and I will forsake them, and I will hide my face from them, and they shall be devoured, and many evils and troubles shall befall them; so that they will say in that day, Are not these evils come upon us, because our God is not among us?
18 And I will surely hide my face in that day for all the evils which they shall have wrought, in that they are turned unto other gods.
In this context, "that day" refers to an extended and indefinite period of time, potentially extending over many years.
Both. Adam experienced a spiritual as well as a natural death.
Well, in those days it was 930 years, nowadays it is more like 93 years! But the basic principles remain the same.
God determined the extended period of life and death. He could have made it an instantaneous death if he had wanted to, but he chose to do it the way he did for a wise purpose best known to himself.
It means both.