The old and new self mean the same as the old and new man. The term "old man" probably refers to the sinful nature with which a person is born. The "new man" is the new nature or new life that God gives a person after they come to believe in Christ. (See: [[rc://en/tw/dict/bible/kt/sin]] and [[rc://en/tw/dict/bible/kt/faith]])
Many of the things Paul encourages his readers to pursue or avoid are not actions but character qualities. Because of this, they may be difficult to translate. (See: [[rc://en/ta/man/jit/figs-abstractnouns]])
Where God dwells is often pictured as being located "above." Paul says to "seek the things above" and to "think about the things above." He is implying Christians should seek and think about heavenly and godly things.