Is the sentence "Why are you smiling at" wrong here ? English is not my first language.
I'm sorry but it's wrong, the 'at' in your sentence shouldn't be there.
"Why are you smiling at" would need something more to be correct. For example, "Why are you smiling at me?" or "Why are you smiling at the mirror?".
Only seem. The noun "smile" is "uśmiech", the imperfective verb is "uśmiechać się" and the perfective one is "uśmiechnąć się".