thank you all for your advice
Wow, I get dizzy thinking about the acreage you all have to work and transform!
It made me realise that my 215 m2 is peanuts and that I shouldn't worry too much about it
I've found a friend of a friend of a friend who is willing and able to do whatever I want
what will probably be: getting rid of the top layer with the weeds and roots and replacing it with sand, soil and other goodies
I will (try to) make photo's along the way to keep you all posted on the progress
Mayo