"多謝"同"我愛你" 的德文應該點講?

Thank you is 'Vielen dank' - there MUST be a 'n' on 'viele', which means 'many'.
Or you could say 'Danke schoen' (literally Thanks already)
I love you - this one is tricky, you would ONLY say 'Ich liebe dich' to someone like your wife (or your long time girlfriend). All other cases, to either male or female, it's always -
Ich mag sich. (I like you)
Be careful not to make a joke out of yourselve!

Typo:
Not "Ich mag sich." but "Ich mag dich."

多謝 = Viel Dank
我愛你 = Ich liebe dich