Don’t worry; it gets better from month to month. I got a TEP at 51 4 years ago. Before that I did a lot of IMs and also competed in championships.
After that I started again very slowly. Especially when running, I paid more attention to quality than to quantity. It was also important to me to do a lot of strength and stabilization.
Today I am fit again and “competitive” up to the middle distance – with max 40-45 running kilometer per week; usually 20-25k.
In my blog (but you have to translate with google or deepL) I have written a few things about it, maybe this will help you:
Stay focused,
Tom W