Fragen über die Beispielsätze mit, und die Definition und Benutzung von "Coff"

A: × I misunderstood that my coff maker had been broken, so I bought a new one.
✓ I thought that my coff maker had been broken, so I bought a new one.

× However, it wasn't right.
✓ However, I wasn't right. (or It wasn't broken)

× it still works well, so I'm about to give my friend it.
✓ it still works well, so I'm about to give it to my friend.

The word misunderstood isn't really grammatical wrong. It just sounds a little unnatural.

A: I don't know the word 'coff'. Do you mean 'cough'?