Scroth exercises are not for muscle building, only stretching and alignment. Check with your Schroth PT about what strength building exercises you can do additionally. It would probably be good for you to work with a regular PT knowledgeable about osteo, separately from your Schroth training, to teach you safe movement. I would highly recommend exploring Sherri Betz's website.
https://www.drsherribetz.com/osteoporosis
She has online classes and privates and is a wealth of info.

When I was first diagnosed, I found a PT who was knowledgeable about osteo. She taught me how to move safely; hingeing at the hip with a flat back when bending and lifting, dead man's roll to get out of bed, etc. Once I knew those things, I could safely work out on my own. I go to the gym 1-3 times a week and am lifting heavier weights than I did when I was in my 20s. Build up slowly, safely and carefully.