I've talked to my Oma about this (she's a native German), and she said she never really noticed but yes, "ig" endings do not have hard g sounds, they sound more like "ich".

I would say either "with" to mean "he is living in the same house as his mother", or "off of" to mean "he is getting money from his mother to live". To me neither "by" nor "on" sound right...

This is an expression which supposedly comes from Marie Antoinette saying it during a famine (she didn't actually say it). But now it is referred to when a rich person doesn't understand or care about the problems of poor people. They aren't literally saying it. In this context, the writer is saying that the people on Wall Street are being insensitive to the problems of the poor, and they don't understand what it's like to be poor.

You would say "I love going out with friends and I don't like staying home by myself." Also, I notice a lot of Arabic/Turkish speakers say "Is this sentence true", but the word is "correct" instead of "true".

"Carriageway" is UK expression so as a Canadian I'm not 100% sure, but as far as I'm aware, a "single carriageway" is a highway where all of the lanes are right next to each other, and a "dual carriageway" means that the two directions are separated by grass or some other barrier.

In Canada/America a lot of us just say "where in X are you from" or if we have already asked where they are from, we just say "where in X?" so we'd have something like this: "Where are you from?" "Australia" "Oh, where in Australia?" "Near Sydney"

In Canadian/American English, "crazy" is equivalent to "insane", but we use "mad" to mean "angry." We only use "mad" as "insane" in specific expressions like "mad scientist" or sometimes when we are trying to sound more literary or "English".