https://www.instagram.com/kyraonig/?hl=en
She is a digital influencer. If you see her posts naa her background looks super realistic. How to acieve such kind of renders inside blender . I am talking about the character but the background and environment . I can render such real character
There’s nothing particularly special about the backgrounds, they’re just photorealistic renders. Nothing you couldn’t do without practice 
As far as blending the character into the background… I honestly don’t think they’ve done a very good job, but it just boils down to using lighting that matches. Doing post-processing like color corrections and brightness/contrast after combing the background and character helps unify them- and adding a very slight color overlay to the image can really help unify things as well. I usually add a 5-10% Overlay, Soft Light, or Multiply of a daylight warm yellow to blend characters and backgrounds
Just have a look at finished projects here on BA with for example additional tag interiorarchitecture 
:
https://blenderartists.org/tags/c/artwork/finished-projects/18/interiorarchitecture