Sentence Variations?

Okay, so as you might know, I have Japanese people that correct my Japanese for me.
So here it is.


ボブ: アリス、どこに行っているの？This one I was trying to say "Alice, where are you going?"

ボブ: アリス、今どこに行っているの？／どこに行くの？／ど こに行ったの？
And here it's corrected to "Now, when are you going?"
But I don't get the different ways of saying it.
Well I get the first one and second one. But that last one with itta no, I don't understand cause it sounds past tense. What do you think?

アリス: 私は先生と一緒に私のアパートに行っていますよ。
Then there's this one, which I tried saying "I'm going with the teacher to my apartment."

アリス: 私は先生と一緒に私のアパートに行くところです。
And this is the correction. I see tokoro near the end there. Now looking at it I can probably figure it out but if you have any pointers on how tokoro is used then please share! Thanks!

First off, what's up with this situation.. haha.

Anyway, it's "Where are you going now?" and the itta part can be used when you're asking someone where they went/they're going if you met them at one point and then they left without warning for example.

Tokoro Indicates that an action takes place, just took place or is about to take place.