Cleaning of a yacht

A little difficult to tell the material in the pic, but if it's stainless steel or chrome it looks like time for Never-Dull. I don't generally recommend Never-Dull as it's an abrasive. Once you use it you'll need to use it more and more. However once pitting and scratches start you're stuck. Once using Never-Dull keep the stainless coated in wax or something like Corrosion-X or Plexus to keep moisture out.

That's not dirt, it is the stainless tarnishing/rusting. Use Collinite metal wax on it as directed with t-shirt material and polish it out. Can also use 0000 bronze wool with the metal wax on it, but I don't think it's that bad.

If SS, spray with "A Must for Rust", an acid that will neutralize and remove the rust. Then rinse and wash/dry, then Collinite Metal Wax.
Don't spill the acid on gelcoat, it can bleach it..

Oops, I just now saw you are in Italy and probably have a different name for the acid product called "A Must for Rust". Same stuff should be available over there too.

What about 000 grade steel wool followed by wax? Crazy?

This

You always work with the minimum abrasive you can get the job done with, which is why I recommend Never-Dull and that only when something more mild won't get you there. Abrasive take off the finish and protective layers on everything. Once that's gone you have a job for life. Often on things like this you can even just leave a spot of Kroil oil on it for awhile to eat away the corrosion, then coat it, but this looks a little past that point.

The resolution on the photo is not adequate to determine exactly what is going on but it appears that the problem is the result of dirt being left in place for a long time. The spots look like corrosion pits that formed under the contamination. If those are pits, all the mouse milk and magic cleaning sauce in the world will not fill in the holes. The pits have to be removed and only (abrasive) resurfacing and passivating will restore the orginal finish.

Agree, and I also noticed horizontal scratches or wear marks. that indicate someone may have got at it at one time with an abrasive, probably exacerbating the problem. Again, once an abrasive is used it becomes all the more important to keep the metal coated with something. Much easier to keep stainless nice than to get it back to nice.

I'm not a big believer in marine products as they're generally weaker and more expensive. So I'll probably get some flack here. Although I do like Spray Nine, Fantastic is just as good. Windex for glass. I like Soft Scub with bleach for stains on decks, everything from bird poop to a burn from a cigarette. I use whatever boatwash is available, but truthfully I prefer Turtlewax. I am a bit fanatical about eisenglass. Never touch it with a brush. Soft sponge (this I get at the marine store) only and then polish it like fine furniture with Plexus. I also coat stainless with Plexus or Corrosion-X. CRC-656 is my main lubricant and grease remover. It also coats stainless good, but is a little greasy to the touch. I coat stainless near the waterline with Boeshield T9. It yellows over time though so don't use it on stainless up on deck. Soft marine brush with rubber fendering, medium for scum by waterline.

If it is real teak you can probably sand some of it out, it will all fade to the same colour in time fresh dents can sometimes be fixed by soaking them with water and applying heat via an iron to steam them out.

It will eventually fade but a spary called K2R is very good at removing a lot of things like that.

I don't know where in Italy you are but there is a good agent called Pesto in Genoa who speaks very good english

For the oil, the best I can think of is teak cleaner, and then teak oil the deck. It should dilute and blend the other oil in. For the rub, as K1W1 suggests sand it lightly, preferably with brass wool.

To clean oil off of teak use K2R.

To clean the rust on the stainless steel use http://spotlessstainless.com