Finally started

I had asked in this group a few months ago about if DDP Yoga helped any of y’all with joint pains and back pains, finally bought into it a couple of days ago and I just did my first work out. I feel ducking great, definitely feel looser in almost all my joints but still feeling discomfort and stiffness in my lower back from a pulled muscle a few weeks ago. What workouts or positions do y’all recommended to help open up my back and promote general lower back strength? Still trying to figure out the app since I’m a little technologically handicapped for a young guy. Appreciate any help and your previous advice and testimonials