The preposition en can be summarized as "to or in," but it's a bit more complicated than that.
French has two opposing families of words that indicate location: the ci family and the là family. These base units are found in a variety of words with various functions, including ici / là (adverbs), voici / voilà (presentatives), and ceci / cela (pronouns).
Devoir is a very common French verb with irregular conjugations and an unusual relationship to some of its English equivalents. Devoir has several meanings related to obligation, supposition, and expectation.