Trouble flattening surface around curves

Hi there! I have a surface of a park site, and am trying to gradually flatten it around surrounding buildings so that neighbours can have easy access to the site. Does anyone know how to achieve this gradually, because at the moment there is a hard transition between the base surface and the ‘flatness’.

Thank you!
flat_around_curve.3dm (887.2 KB) (7.7 KB)

What does this mean?

Sounds similar to this one except your edges are not well defined.

Also this:

I’m not sure this is correct. Probably should sleep on it and look again in the morning… but I since no lives depend on it (I hope!), I’ll post it now. (37.0 KB)


Thank you so much that’s perfect!!