It had even smaller arms than T.rex and pretty useless ones. They were tiny and the only motion it could really do with them is rotate them.
This theropod didn't need them, it could run quite fast for a theropod this size, so it surely was one of the apex predators of its time.

Its horns could be really big but that's speculative. I like to draw them a bit bigger than their boney base. (The rest of the horns are made out of ceratin, the same material as bird beaks. And kind of the same material as your finger nails, also the material most animal horns are made of.). They most likely worked as display structure to attract mates and show how healthy the animal was. It may have also served in combat between members of the same species.