Texting and chatting with girls is always impossible. What happened?

All right. First, let's see what kind of person she is. But generally speaking. Anyway. It is polite to reply to other people's short messages. Don't reply to text messages or say you need to be busy. Or I don't have feelings for you. Either you chase too hard, that's what people do. The harder you chase, the less she feels. Leave it for a while, don't deliberately keep a low profile, and don't send it until she answers you. Change the subject next time. Girls still like free and easy. You can't be too nice to her without saying something nice.