I’d like something similar to the ML and FL in it. Arranged cohabitation and etc. Please don’t recommend me  “Cinderella and the 4 Knights”, “Meteor Garden“ all versions and “1%of anything“. FL has to save a rich granny or grandpa or help a rich guy in any way.

I haven't seen Shining Inheritance (2009?), so could you explain a bit more what you want?

Perfect and Casual has a contract marriage in order to fill the wish of the ML's dying grandfather. The ML isn't hugely rich.

She saves their granny with a road accident, and they have to marry her to have their inheritance back.

« Jang Bori is here » gave me similar vibes to Shining inheritance. You can also try the recommendations on the drama page.