It has a medieval-like setting.
She has to get married to a nobleman (Marquis, Duke, I can't remember) she meets for the first time during the wedding ceremony, held without guesses and without wedding party.
He has a bad reputation, he's told to be a cold scary evil bad person. Actually his father was that, to the extent he killed his own wife (the ML's mother) and kept his son locked up in his room until his own death. The ML is a kind guy, he's not cold but very shy. During their first night he remains hidden under the sheets and communicates with her writing instead that talking.
Please, help me! Thanks in advance!

I've lost this yaoi manhwa: the MC is inside a game and he has to make the ML falls for him. They're both black-haired; the ML is the usual cold alpha CEO; the MC has to loving alpha brothers; there also are three boys with coloured hair who become friends with the MC.
There are more chaps uploaded but not in mgg, here it is
https://www.mangago.me/read-manga/how_to_win_over_an_alpha_male/
Thank you! Have a nice day