I have watched To the beautiful you, School 2013, I hear your voice, Monstar. I am currently watching Shark, Master’s sun and Scandal as well as waiting for The Heirs to start. Any suggestions similar to the ones I watched or are watching? Thanks in advance 
I loved ‘To the beautiful you’ and i want to watch School 2013 but i’m lazy lol, well, i don’t know if similiar, but if you like romantic-comedy drama you should watch ‘Ramyun Shop Flower Boy’ (something like that), Love Rain (one of my fav. dramas ever) and Secret Garden (another fav. drama) 
I’m going to say… Reply 1997, Shut Up: Flower Boy Band and God of Study.
Also mayyybe you might like You are Beautiful, Coffee Prince, Goong (Princess Hours), Flower Boy Next Door, Flower Boy Ramyun Shop
Good elections. School 2013 it’s very very good drama. And I Hear Your Voice it’s excellent.
My recommendations:
Romantic: Queen In Hyun’s Man
Drama: The Innocent Man
Period: The Princess Man
Comedy: A Gentleman’s Dignity
Family: Can you hear my heart?
Fantasy: Gu Family Book
Thanks for all the recommendations, once I finish the ones I’m currently watching I’ll check some of these out.