However, if two people have a good relationship and have reached the point of talking about marriage, it is normal to entangle. After all, emotionally speaking, it is really difficult to choose between being a girlfriend, perhaps a partner who will die together in the future, and buying a home that will shelter you from the wind and rain for a lifetime. Look before you leap. If you do decide to pay her back, try to get your girlfriend to write an iou and lend it out by bank transfer. After all, 400 thousand is not a small sum, and there may be support from your parents. You're not married. I'm sure your girlfriend can understand. In case they are not together in the future, it is also convenient to safeguard their legitimate rights and interests.