Didn't understand what are you talking about

Didn't understand what are you talking about这是病句吗，应怎么改

你的意思是说不知你在说什么，但语法是错的，因为没有主语，人家只能理解为祈使句，这个句子就不能理解，要加上I。即I didn't understand what are you talking about

应该用simply。因为这句话 “i can’t understand what you are talking about.”已经是完整的了，什么都不缺，此时只需要一个副词来修饰即可（表明程度、方式、状态等），用来限制、修饰“understand这个动词。 另外比如们很熟悉的这句话：listen to me carefully. 本来listen to me 已经是一个完整的句子（祈使句），那么怎样听呢？后面加一个carefully这个和副词，表示是”认真地听“，用来修饰listen这个动词

what are you改为what you are 宾语从句用陈述语序，主谓不用倒装

你好！你要是想表达过去发生的事情，时态应该改为一般过去时： Didn't understand what were you talking about. 如果是谈论现在发生的事情，用一般现在时： Don't understand what are you talking about. 希望可以帮到您

可以改为：I don't understand what you are talking about. 坚持用过去时态的话：I didn't understand what you were talking about. 后面的语句需要用陈述语序，不能用疑问句语序。