Those are most likely text messages.
"Sya lng gusto k" - The proper phrase would be: "Siya lang ang gusto ko" = He/She is the only one I like/want.
"yarehh kahh" -> "Yari ka". An idiomatic expression, meaning "you're toast" or "you're in big trouble".
I hope I am wrong, but the impression I get is that the person who said these might be angry about something or towards someone.