can someone recommend me some horror mangas/webtoons?

Oh my you should def check this out. This is by far the best psychological horror I've read. I hope you'll like it and hear from you soon if you liked it. Enjoy! :)
http://www.mangago.me/read-manga/bastard_hwang_youngchan/

Also this one, created by the same author. But read this after Bastard :)
http://www.mangago.me/read-manga/sweet_home/

http://www.mangago.me/home/mangalist/235645/

Hwaja is great!!

Pumpkin Night (a new manga & damn there's a lotsa blood)
http://www.mangago.me/read-manga/pumpkin_night/

thank you all for the recommendations!! i’m reading Bastard right now, and i’m currently on chapter 43, and i simply cannot get enough. thank you for recommending me such a good story!!

My pleasure! This manhwa needs to be spread. Enjoy