Do you have access to a gym, more specifically a barbell? It's the simplest and easiest way to increase functional strength.
I started lifting/doing HIIT when I hit 40 and within 6 months, 20 years of back-issues virtually disappeared and my overall health become much better.
Blood pressure, which was creeping up and needed drugs to be managed went back to normal within the same period, much to my doctors amazement.
Sure, I also lost some weight, but most importantly, I felt much better. I stood taller, felt more stable, etc.