Käännös - Brasilianportugali-Saksa - dia inesquecível.amo mto

In German in contrast to Brazilian Portuguese one always start the sentence with a capital letter. Also, it might be a "typo" but the last sentence should be:
"Liebe dich sehr"

but there is no personal pronom for the object.

=> Liebe dich sehr <|> Te amo muito / Amo você muito.

only "amo muito" => "Ich liebe sehr".

I think, it could be related to the "day". (I love the day a lot)

Franz: Amo você muito is a very rare way to say that in Portuguese (only when you want it to have an emphasis or explain something) like "Amo você...e amo muito". The right way should be "Amo muito você".
Here it could be "Unforgettable day, I love it a lot", "Unforgettable day, I love you a lot" or even "Unforgettable day, I love a lot (as s/he was totally "open-heart" )". You must put those in the remarks field too.

Heidrun: you have my bridge already.

CC: iamfromaustria