What is the difference in the finnish formulation between "You are a really good friend" and "You are really a good friend"? In google translate both English phrases lead to the sentence above. I would expect there to be a way to express that someone is really a good friend. Does anyone know?
Hmm, if by "you are really a good friend" you mean "you are, really/truly, a good friend" then you could try placing "todella" elsewhere in the sentence, or add -kin for emphasis, e.g.
Sinä todella olet hyvä ystävä.
Sinä todellakin olet hyvä ystävä.
"Todella(kin)" could also come in the beginning of the sentence, but this placement is slightly more unusual.
On the surface, it would seem to me that the given Finnish sentence should lead to either English translation, and context might be the only way you could tell the difference. I put "You are really a good friend" and was marked wrong. If there's a reason for this other than "it hasn't been implemented yet", I'd like to know what it is.
My understanding is that they say the same thing: "you are". However, since the -et ending of "olet" is unique to the 2nd person, you can shorten the phrase to "olet" alone and since it has that -et it imples the "sinä", so you don't need to write it.
In English, it would be like writing "am hungry." Since "am" is exclusive to the verb form "I am", you know "am hungry" is implying "(I) am hungry" so you don't need to actually write the "I". You would never mistake it for "we am hungry."
You can do the same thing with "Minä olen", since "olen" is similarly exclusive to "minä" just the way "olet" is to "sinä," but if I understand correctly, "I" and "you"(singular) are the only instances when you can do that.
HOWEVER, there may be colloquial nuance to just saying "olet," or fully writing out "sinä olet", that I'm not yet aware of. Is one conspicuously informal? Is one snobbish? I don't know. Hopefully a native speaker will come along and weigh in on that.
You can actually leave out the pronouns in 1st and 2nd person plural as well:
(me) olemme - we are
(te) olette - you are
However, with 3rd person singular and plural the pronoun is nearly always included, so it's safest to say that you always have to write/say it. The reason for this is that with both "hän" and "se" the verb conjugates the same, and this is also true of "he" (they, people) and "ne" (they, animals, things etc.).
hän on - she/he is
se on - it is
he ovat - they are
ne ovat - they are
In spoken language you could say e.g. "se on" (he/she is) or "ne on" (they are, of people, animals, things etc.), so even there it's important to include the pronoun in 3rd person.
As for the formality or informality of "olen/olet" vs. "minä olen/sinä olet", it depends slightly of the sentence in question, but generally there is no difference whatsoever. "Olen" is certainly not less formal than "minä olen".
In spoken language, instead of "minä olen/sinä olet" or "olen/olet", you might more often hear e.g. "mä oon", "oon", "mie oon", "mää oon", "sä oot", "oot", "sie oot", "sää oot" etc. depending on the region. One can notice that even in those forms you can easily spot the -n and -t endings in the verbs. You can say that these forms are more informal, but you certainly aren't considered rude if you use them in everyday conversations.