How do I (20M) build a good sibling relationship with my two half sisters (14f) & (12f)

For context I found out three years ago that my father wasn’t my real father and that my real dad left when I was really young. I then found out he had kids with another women his ex wife. Recently about 2 weeks ago the ex wife reached out to me and wanted to introduce me to them both, they previously didn’t know I existed until last week. I went to there city and met up with the two of them and their mum. It was rather awkward but nice and both of them and had fun. I messaged them after the meet saying it was nice to meet them and I would like to stay and touch and meet again. They both agreed to this and want the same. Although they both have really bad anxiety and I think they are struggling with messaging me as they have been opening my messages and not replying. I am unsure whether I am rushing into this and should let them take their time and stop messaging them. Am I being to pushy or should I show them that I am here for them? I’m unsure whether it’s a healthy balance as they haven’t had as much time to process they have an older brother as I have. I’m stuck on how to handle the situation. Any advice would be appreciated.