Hey guys! Could you recommend me some good BL mangas about unrequited love becomes requited or sex friends turned lovers type?

Also anything that has royalty or president-secretary relationship.

recommend me a lot guys!! 😛

Try royal fiancé for the royalty, and Kimi no Kao ni Sasu Kage for the unrequited love 🙂

Unrequited Love Becomes Requited
Yorokobi wa Ude no Naka - This is my favorite story of unrequited love that at last becomes fulfilled. It is a follow-up to Yorokobi wa Hiza no Ue, but you don't have to read that one first unless you want the background.
Dare ga Omae wo Suki dato Itta, omg, almost forgot this one, also excellent (1st story)
Empty Heart - MINASE Masara does this well
Koisuru Boukun is a famous example
Hand Which, really good
Akanai Tobira, also SUZUKI Tsuta
You could search for genre 'Yaoi' and category 'Unrequited Love Becomes Requited'. I found that many of these, as I recall, were more a matter of slow romance. Some of these may be tagged only as 'Unrequited Love', so you should check that category as well.

Royalty
Crimson Spell
Ouji-sama Game, Ou-sama Game (TAKAGI Ryo), and Kaizoku Game
Un Carnet de Bal - more nobility than royality
Yaoi + category 'Royalty'

President / Secretary
I've read some like these, but don't recall them now. A search for Yaoi and Secretary would probably get you most of them. You could try Secret Diplomacy, about a diplomat and his secretary, super-hot manly men, but unfinished. 😢

Long Vacation is just a (smutty) oneshot and nothing much happens but I find it worthwhile, if you're looking for sex friends. Check Udagawachou de Mattete yo. by the same artist, for unrequited love, maybe? Well, it's some kind of unrequited love anyway, haha.

It's the Art of Time, it's the Art of Life--
Of the player and the craftsman,
Of the writer of songs, of the creator of love,
Of those who will follow, of those who led,
There's no other way in the world ahead ♥