elongate:
Ausdehnen (horizontal), Mund ist breiter als normal.
(The mouth appears to be longer than usual in the horizontal plane)

de-elongate:
Zusammenziehen, Mund ist kleiner als normal.
(The mouth appears to be shorter than usual in the horizontal plane)

narrow:
Lippen sind schmaler, enger (vertikal).
(The red part of the lip is less visible or narrower than usual = opposite of widen)

widen:
Lippen sind breiter.
(The red part of the lip is revealed more or wider than usual =opposite of narrow)

flatten:
Lippen erscheinen abgeflacht zu den Zähnen hin.
(The lips appear flattened against the teeth. They protrude less than usual. Does not involve sucking in the lips)

protrude:
Lippen vorgestreckt, geschnürt.
(The lips come forward or out away from the face more than usual = opposite of flatten)

tighten:
Lippen sind gespannt, gestrafft.
(The lips appear tight, the lips are not relaxed or loose. The muscle within the lips has contracted)

stretch:
Lippen sind auseinandergezogen und die Haut ist wie ein Gummiband gedehnt.
(The lips are pulled and the skin stretched like a rubber band)

rolled in:
Lippen sind eingerollt.
(The lips are turned, or rolled, inwards, disappearing entirely or almost entirely, but they are not tightened, pressed, or stretched)