着 — a state that stays

The rule 着 after a verb = a lasting state: 门开着。 (the door is in the open state)
Compare: 他在开门 (he is opening it, an action) ≠ 门开着 (it stands open, a state).
V1着 + V2: doing V2 in the manner of V1 — 他站着说话。 他笑着说。
Negative: 没(有) + verb + 着 — 门没开着。