Problem of sound insulation in terraced single-family house

In July 2015 we bought a semi-detached house through a developer. Each house has its own walls, and fire protection wool is located between the houses. There is no basement.

What sound insulation level is specified in the construction description? What does the double-leaf partition wall look like, which type of stone, what thickness, what surface weight, how wide is the separation joint (30 or 50 mm)?
How is the roof connection to the partition walls executed? Is the separation joint between the foundation and the roof covering continuous without gaps?

Without knowledge of the building's structural engineering and only as laypersons, we should determine positions for sound insulation measurements ("by floor hammer and loudspeaker") in our house and in the neighbor's house.

You had to determine the position of the standard hammer impact device, not the expert? Quite unusual, the expert is usually familiar with the critical constellations.

Unfortunately, these values were therefore not sufficiently meaningful, so the developer must take action.

What does that mean in plain language? Were guideline values (whichever, see construction performance description) met or not? "Not sufficiently meaningful" basically does not exist here.