Learn German: Ein Missverständnis passiert schnell. - A misunderstanding happens quickly.

The prefix miss- adds a negative meaning or shows that something went wrong, just like 'mis-' in English. Here, it is attached to Verständnis (understanding), which comes from the verb verstehen. Together, they form das Missverständnis (the misunderstanding).

Why does the sentence use the neuter article ein for Missverständnis?

Nouns that end in the suffix -nis are usually neuter, which is why it takes ein. You will see this suffix often when verbs or adjectives are turned into nouns, such as das Geheimnis (the secret) or das Erlebnis (the experience).

I thought passieren meant 'to pass'. Why is it translated as 'happens' here?

The verb passieren is a common false friend. While it can mean to pass a physical location like a border, its most frequent meaning in everyday German is to happen or to occur. So passiert schnell simply means happens quickly.