Concreter should have protected the surface if rain expected

Is there a reason the concreter can’t grind and then patch the low points and put a skim coat over the top? You haven’t lost functionality just looks so the solution can just deal with appearance.

He said he doesn't do that and offered to paint it.

You can’t paint while there is a dip in the middle, and paint won’t give a lasting finish especially if there is true delaminating. Try and negotiate a reduced rate or refund and then source another concreter for a grind to stabilise the top layer and a skim/top coat to get a better finish. Good luck.

Concreter should be responsible till it’s set, unless otherwise agreed. May need to be pulled up and relaid.

Yes I agree with all the above but I'm looking for suitable products for repair. Thanks