Mahogany porch

I have a mahogany floored covered porch. It was sanded and refinished about 4-5 years ago, but I have no idea what was put on it. I know it was a clear or light translucent coating. The outer edges are all grey, and some of the wood has green stuff - mold? - on it. The interior for the most part isn't bad. High traffic area shows wear, and step is very bad with water and wear and the green stuff. Should I sand down the whole thing, then use your re-store kit? No sand? I'm not sure what to do here. I want to put a TWP product on it, to keep it from further degrade but need some help with this one. Any suggestions would be appreciated. The porch is 10' wide and 50' long - both ends have sun/water wear, and the leading edge needs the green stuff and the grey sanded, i think..??
Thanks,
Ralph