Most of my problems are age related - I’m a lot older than you - but they stared about your age. For what it’s worth:
Begin with the chair exercises as others have said. Work on your breathing.
Breathing properly makes exercise far more effective. This is the ideal time for you to focus on it. There’s lots of advice online.
Join a gym and get advice from a PT as to how to use specific machines safely and effectively. My main problems are with knees and back, but once I worked on strengthening the relevant muscles they improved greatly. Cardio I get from the recumbent bike, the rowing machine (which I know how to use properly because I used to row, be careful if you use one as poor technique can make them very damaging) and the cross trainer, no impact. I recently had a heart problem and was able to keep exercising while ill by doing what I felt comfortable with. I go to the gym three times a week if possible.
I do yoga type stretches and some light free weights daily. I got the stretches from a book decades ago, but you could find someone to advise you. This makes a real difference to my strength and fitness, and I have shorter or longer routines depending on how I feel and how much time I have in the morning.
I try to walk for at least 30 min every day. I stopped running years ago, it was very damaging for me. On uneven ground I use a walking pole/stick, which gives a third point of contact and helps avoid stumbles and twisting my knees.
I find a soak in a hot bath two or three times a week very helpful for aches and pains and I use a painkiller if I need to, for me ibuprofen works best (not necessarily every day or even every week, but as and when).
I intend to take HRT for as long as possible. Luckily my GP is OK with this.
By using the methods above, I’m pretty much in as good shape at nearly 70 as I was at nearly 50.