Removing / Reinstalling Curbstones

Dear forum, the street in front of our house is currently being torn up to lay new pipes. For space reasons, the construction pit extends slightly into our property, where there used to be a paved footpath and additionally an edging for a flower bed ... or rather was before the construction work.

The construction company has been commissioned to restore everything to its original condition afterwards. The curbstones of the footpath and also the natural stones of the flower bed edging were each set in a normal concrete foundation.

Now more stones have been removed than necessary for the construction pit. The stones are gone, but the concrete foundation is still there in these places. How should this be restored so that it also holds in the long term? I am not an expert myself, but I imagine that you cannot simply reset stones into an existing foundation after they have been broken out? Is it sufficient to remove the upper part of the foundations (with what tool? demolition hammer?) and then reset the stones with new concrete? Or should this be done in another way?

Thank you in advance for answers and comments!

I would be surprised if there is a proper foundation (40-80cm deep) there. Curbstones, especially for sidewalks and flower beds, are usually only fixed with a back support (concrete wedge). The concrete then goes 10, maybe 20cm deep. So it's not an issue if they break it off and then fix it again with a new wedge.

Thank you for the response. Under the stones it is about 30 cm, additionally with back support. So not necessarily something you can just get rid of with a pickaxe (?) ... How much of it should be removed before the stones can be reset? Preferably everything? Or the top 10 cm?

So I would say that 20 cm is enough, but since the company is doing it, I would demand that everything be redone. They certainly have proper equipment and not just a pickaxe.