Ei kestä, you're welcome!
As to the question, my German is a bit rusty, but I got the general idea.
Minä rakastan sinua = Ich liebe dich, and this is the most common form. You can actually use this first also.
Minä olen rakastunut sinuun ~ Ich habe dich lieb, not that common and can really only be used once, the first time you mention the l-word to her. But it's still on the same level. Let's give a few differing degrees of affection...
Minä olen rakastumassa sinuun = "I'm falling in love with you." On the way there.
Minä olen ihastunut sinuun ~ I've fallen for you -- when you don't dare mention the l-word yet but want to bring up the affection. Again, this sounds weird if used more than once, if you want to keep it on this level before "love", a natural way to say would be "Olet ihana" (You're wonderful) because the simple present "Minä ihastun sinua" (the noun "sinä" in partitive) would be complete nonsense, and grammatically correct "Minä ihastun sinuun" (sort of semi-continuous, the noun "sinä" now in the illative) is really awkward way to say separated from other attributes, whereas "Minä ihastun sinuun päivä päivältä enemmän" (~"I'm falling for you more and more every day" -- sorta in-between future or continuous present) would on the other hand make perfect sense, even though it may sound a bit cheesy.
Minä olen ihastumassa sinuun ~ "I'm falling for you." On the way to the awkward level above...
It's a bit difficult since the tenses (or rather, their use) in Finnish and German (or English) don't fully match. German uses the perfect and past participle much more, while Finnish idiomatic translation would use present or imperfect more often. The continuous present tense (as in the above examples the -ssa suffix) is grammatically correct, but is sometimes awkward, sometimes useful. Also, in Finnish the future tense doesn't even exist in formal, only in spoken language - it relies on the use of the auxiliary verb "tulla" (to come), whereas the grammatically correct "future" would be the simple present tense.