Just wanted to say congratulations on launching your first project! This is quite well done.
One piece of feedback: I'm sure your partner trusts you and has asked you how you came up with this routine, but we random internet users can't do that and the site currently doesn't do anything to convince us that we should follow this routine. One way you could build trust with your users is by including a link to the source for the routine, or a short explanation of why you've chosen these stretches, in this order. Another way you could approach the problem of building trust is by making the routine adjustable or editable, or allowing the user to pick between different routines or exercises. I think it will be hard to get someone to commit to doing 15 minutes of stretching, every day, without doing some kind of education or somehow building this trust.
Again, great launch / v1, and congratulations! No need to try to make it anything more than this if your target demographic (your partner) is already happy :)