To the girl I like, I don't answer the phone for several days, but I don't reply to the text message. What should I do and continue?

don't make harassing phone calls and send harassing text messages all the time.

You can send messages of greetings and concerns regularly, such as checking that the weather will cool down tomorrow, reminding her to add clothes, and so on. What is important for chasing girls is not what you say, but what you do. As long as you do and pay, you will get good results. I wish you success.