Hello community,
how can I solve these hard light gradations on my wall mesh?
light is a static point light!
PLEASE help me! THANK’S in advance! 
Lower Static Lightning Level Scale (inside the lightmass settings) value to 0.1 (it will explode baking time). 
As NasteX says, use lower Static Lighting Level Scale. Often even 0.5 can help a lot. And set higher indirect lighting quality too, in the same World settings → Lightmass tab. It’s an issue of UE which won’t be solved (according to developers, it’s a matter of baking optimization).
Regards,
Oskar