Traduko - Nederlanda-Brazil-portugala - Ik zag je wel vndaag op de open dag met je...

"open day" => "dia de acolhimento"
(inauguração <= opening)

Eu vi você bem, ou seja, eu vi você e você estava bem.

No final, "I think i've changed too much for you"
A tradução correta seria:
"Acho que eu mudei demais POR você."

"Open day" is a day when the public is allowed to visit a place to which they do not usually have access. The most acurate in Portuguese would be:
dia de (livre) visitação pública

I chose inauguração for being a single word with a very similar meaning.

For all right, the expession means many things, the most likely here is "for sure". I don't think the author was talking about what she looked like, but just stating that he did have seen her.