Do you need to be rude when giving an answer ? First "to suck at something" is a rude formulation and, second, we are still beginners at this points of the exercises so YES, irish pronunciation still sounds like being said with a mashed potatoe in the mouth and most of us don't hear it perfectly yet.
"is sadness on him" is just word-for-word translation. Irish syntax is different to English. It's VSO https://en.m.wikipedia.org/wiki/Verb–subject–object
You are confused about two structures using tá and ar: "Tá ar+X VN" where X is a subject and VN is a verval noun means "X must V", while "Tá N ar+Y" where N is a noun and Y is a noun means "N is on Y" ,and in the particular case of Y being a subject and N a feeling (like sadness or joy), it means that "the feeling N is on Y" which will be further and correctly translated in "Y is A" where A is the adjective correspinding to the feeling N.
Examples : Tá air snámh = He must swim. Tá brón air = Sorrow/Sadness is on him = He is sorry/sad.