[verb] + [result] + [object] + 了
没 + [verb] + [result] + [object]
A result complement is a second word straight after the verb that says how the action came out. The verb names the action, the complement names what it achieved: 洗 is "wash", 洗干净 is "wash clean".
English often packs the attempt and the result into one verb. Chinese splits them: the verb alone says you did it, the complement says it worked.
A result that didn't happen takes 没, and 了 drops out.
不 between the verb and the complement, as in 听不懂, is a different pattern that means "can't" – the potential complement.
The verb and its complement stay together. 了 and the object come after the pair.
The commonest complements – 完, 到, 见, 好 – each have their own point.