Andy yer land is 336 sqm.. building code here more or less expects you to be about 2 meters aways from yer neigbors boundry, the front road.. at least enough to park the length of yer motor.. so figure that one out and deduct the shack you want to keep, times the remainder surface you want to build and voila you got the checkbin ... now you can go get yer self an architec/engineer and they'll take care of the rest... sic et sempliciter