Help - I want to help a friend but I don’t know how!

Hopefully it lets me upload the photos- my lovely friend has let me stay with them (don’t worry it’s not the weird nappy story lol) and in return I’m cleaning. However I’ve always cleaned a bit each day and occasionally big clean. These guys don’t clean unless they can visibly see the dirt (weird no?) so I’m facing some dirt I haven’t faced before - weird brown stuff around the kitchen taps and greyness Around the bathroom taps. Please help, thanks everyone