short means scurt not scund
No, that means also "scund", if you talk about people, and if you talk about objects or the length of something, then means "scurt".
scurt is for length of objects,
scund describes the height of someone.
Can't I say, "Eu sunt scund, nu am înalt" ?
"am" is english, you need second "sunt". If you used aux. vb. "to have", then it's not correct.