FYI: In some context, "coming" seems to fit better than "going". This sentence can be used when someone is waiting for you at the door and asking, like: Where are you? We'll be late! And you answer from your room, hastily putting on your clothes: Да, я уже иду! Or just: Иду-иду! (Coming!)
The more direct translation of "come" - "приходить" - wouldn't sound natural here. You wouldn't say "Я уже прихожу".
Is anyone else having trouble differentiating which syllables are stressed in some Russian words? Every time I hear у-ЖЕ it sounds like У-же to me, and че-ло-ВЕК sounds like че-ЛА-век, etc. I have no trouble hearing the reduced vowels; it just sounds like the wrong syllable is being stressed sometimes. I've never had trouble with this in other languages. Is it me? Is it the audio? I have to look up each new word on Wiktionary to make sure I'm stressing the correct syllable.
Meaning is context. "Yes, I'm already going," in the context of attending class is natural but in that context it's synonymous with "yes, I already go" In the context of having decided to go to a party or event, is natural. But that's describing an event in the future so would be synonyms "Yes, I'm going."
However "Yes, I'm already going." absent context or as described in olimo's post about some one waiting for you to catch up it doesn't work in English but does (apparently) in Russian. "I'm on my way," "Coming," or "I'm coming," do work for that concept structure in English.
This seems a case where the two languages map concepts slightly differently which is fine but for us to get a proper understanding of the Russian map we need for "Yes, on my way," to work.
Иди ("ee-dee") is the imperative of the verb идти. Like if you're giving the command or asking someone to go ("Go to the store", "Go outside!", etc.). It is second person singular (ты), for informal conversations. Иду ("ee-doo"), is the first person singular (я) conjugation, meaning "I am going", or "I go".
No. In English you use "will" or "be going to" to express simple future tense, but with your example, you would just use the Russian perfective verb by itself to express that, without will or be going to (or Amelia could be lazy and just say "schas" and it would be implied she's going to stop).