'parts inside air cleaner housing make up the then current Mercedes oil/air
separator (hose from the top of the valve cover supplies varying supply of
oil to the separator[then the oil drops down into the oil sump.])Look underneath
you'll see the oil return tube to the sump(there will also be an oil return line from
the Turbo that is separate.)

The oil line you picture in front of the A.C. compressor feeds oil to the oil cooler
(a radiator for the engine oil.also visible in your picture)

Oily Greasy round thing is a rubber sub-frame bushing.[I believe](It'll not like the exposure to petroleum products and will probably have a shorter life span as a result.)