They are not interchangable. Think of '-da/-de' as a direction of movement. Ev and durak are close to each other, but neither are moving. Whereas göl çok yakında gives you an impression of where you will eventually be. Think of the two situations. If you were travelling then göl çok yakında. If you lived nearby then göl çok yakın. The fact that we have arrived this far in Duolingo is a feat in itself. We are at a scism, where we do not know enough to speak the language, but we can see its applications through slight inflexions.