Hello there @Gigor-r!
Considering your scenario, I think what you are looking for is the Landscape Patch Tool. This is a beta plugin that will allow you to adjust, deform and align the landscape automatically based on your house mesh.
The first step is to enable both plugins, as seen here:
After implementing and restarting the engine, you should be able to adjust the landmass using the options from Outliner:
There’s also a video guide demonstrating the tool, hope this helps!
