手表坏了应该是说 my watch has broken 还是 my watch has been broken

应该是my watch has broken应该用主动的,因为他没有具体的语境说这是被人弄坏的

My watch doesn't works

应该是my watch has been broken
手表是被弄还的所以要用被动
至于the car broken down是一句错误的句子。要改为the car has broken down才对，表被动。

其实可以说成 my watch doesn't work
如果你想选用broken 还是用主动态比较好~

觉得是 My watch is broken..

My watch doesn't works或者说My watch is dead都比较地道