recovering from covid

my singing partner and i are recoving from covid. my partners voice is weakend any suggest to hepl recover and heal his voice. I have been doing  warm up and drinking waater and herbal teas. My singing partner has been singing and proforming for 40 years. I have only been singing for 2 years

Please see this lesson!

https://www.youtube.com/watch?v=U2ASxAblWss