"My experience from the trip was excellent."
Translation:Η εμπειρία μου από το ταξίδι ήταν άριστη.
First of all, here "excellent" applies to "experience" so it's an adjective, whereas τελείως is an adverb. Also, τελείως means "completely" and not τέλεια that means "perfectly". Τέλεια also happens to be the feminine form of τέλειος that means "perfect" (and not excellent). ;)