Why can't I understand what everyone is saying? Is it too lacking in knowledge?

I don't understand this. This is the label you put on yourself. What is the specific content of their speech? I don't think there is anything particularly complicated about cars or houses. Next time, tell yourself that you can understand, then listen carefully, and then you will find that you can understand, but if you assume that you can't understand, you won't listen carefully, which will lead to a vicious circle.