What does it mean to have a house and a car? My relatives and friends told me that it is impolite to say these things.

If you can say this sentence, such as a simple truth, I have a house and a car, then hearing other people's eyes may mean that you are showing off, that is, showing off your wealth. In another case, you ask people if they have a house or a car. Maybe there is a problem between you two, and people may think that you may be more realistic. So it's best not to say this topic directly. Maybe you can consult, say, talk, and then suddenly mention that. You can't ask whether you have a house or a car, whether you live or rent a house or something. Maybe it's better to ask alone, don't ask deliberately.