I mean grammatically that's not incorrect. But you didn't really answer his question. He asked "why were you late to get back home from the gym" not what you did after the gym. So, he expected you to be at home earlier. Usually I would say: 1) after I was done, I didn't wait a single moment to rush back home. 2) I didn't wait a single moment to get back home after I was done. "I didn't wait a single moment" + to do what + rest...

That may have been a non-native speaker saying "thiSH year". Usually you would hear "thisssss year" when we speak slowly.

我是大学生。 我很喜欢学中文和英文。 我游得很快 。 我在大学游泳池锻炼。 也许有中国人可以纠正你的写作。 "还我参加比赛... 还累因为我有很多上课。今天我学得德国，中文， 还英文学好好“

I don't think there is a problem with changing them, but you will rarely ever come across this phrase in speaking or writing. Usually we say something like: "It's not in my nature to do so" or "It's not in my nature". I have never heard this before: "You don't have it in your nature to be so." But I don't think it's incorrect to say but extremely rare to come across. I usually come across: "You don't have what it takes to be so" and "You don't have it in you to be so".

Karl has answered it pretty well. - I think "or is it" raises doubt that you are unsure or you want to raise a different perspective. Examples: 1) Girlfriend: "It's time to start working!" Boyfriend: ”Or is it?“ *starts to goof off and have fun* 2) "This is a hard question, or is it?" ( I think this problem is hard but it could actually be easy. I'm not sure ) - "what if we were to embrace the concept......" You cannot omit "we were" but you could omit "were to" in this instance. "what if we embrace..." and "what if we were to embrace" is correct. Perhaps an English major can tell you the difference in meaning between these two.

There aren't really any differences between "as of" and "dated". We don't say: "as of dated (date)" as this is incorrect. "dated as of (date)" is correct but redundant. "as of" can be shortened to "of" in this context and placement. "dated" / "as of" / "of" / “dated as of" + (date) are all correct in this context.