Shouldn't there be a comma between κάνεις and Ελένι? I don't know much about Greek punctuation, so I'm basing my question on the English translation, which requires a comma.
Yes, that is a fine translation. I've added it to the Incubator. Thank you.
How about "What's up Helen?" Seems a very common English translation of the same sentiment.
No, τι means what and τρέχει is the third person singular. (Εσύ) τρέχεις Ελένη is 'are you running Eleni'.
Would "what are you making Eleni" work as well? Seeing as that verb is used for making things
How does "Τι" translate to "How?" I thought it meant "What?" So, I don't understand how it could mean, "How are you?" as well as, "What are you doing?" Also, does that mean, "κάνω" is technically "to do" and "to be" ?
You're right. Literally it means, "What are you doing?" Colloquially, however, it is a much more common way of asking how someone is doing than the literal, Πως εισαι; Sort of like how "What's up?" could be an inquiry into someone's emotional state in English. The short answer is, Τι does not translate to how at all, but the sentiment overall is most like the english phrase, how are you?
Anyone know the difference between τι κάνεις and τι κάνετε? I thought the latter was closer to "how are you"?
The only difference is that the first is singular 'you' and the second plural. Check a conjugation table for the verb κάνω or the Tips and notes for the verb δίνω under Present 1 (Tips and notes are available only on the full/desktop website version, they're really good, make sure to read them!).
Also, my understanding is the plural form is more polite/formal. For example, when addressing a stranger, an elder etc.
That is correct. The plural form is used for politeness even when addressing one person.
This example needs a coma after κάνεις because is a little confusing. Please
Yes, that's the grammatically correct way. Nevertheless, Duolingo does not mark wrong sentences lacking commas. I think that this cannot be confusing, though, since the sentence can only mean one thing. Even if a comma was added (and I agree on that), the displayed sentence will remain the same, since it can't be edited, so...