Blown up deadline and I choose a large bite to chew
Just narrow the scope.  It is normal for students (and advisors) to make too broad of a scope.  As they get into a topic, they realize it is too much "real estate" to cover.  

Personally, I would just write up what you have and modify the introduction to have a smaller objective.  But perhaps things are more strict in Europe.  But it would be very normal for a US doctorate thesis, even, to morph quite a bit.  

The other advantage of writing up what you have is that you (and the advisor) are then looking at a tangible object.  Versus arguing about something in the abstract.  When you both look at it physically, it may look like enough.  Plus you need to write it anyways...so it doesn't hurt you, the time to do it.  [This applies to the work world as well.  Don't underestimate the value of a "half a loaf", especially a tangible one that you are looking at.]