That’s the more traditional way of using “in order.” So, for example, you can put your books in alphabetical order. You can arrange invoices in order from oldest to newest, etc. The way we described it in the video was more to say something was complete and correct. In this situation, you could say that your boss wanted the bookshelf in order, if that (to him) meant that all the books were arranged correctly.

In this case, you can use either the verb “get” or “put.” For example, “I need to get my documents in order, as I will move to a new apartment in November” or “I need to put my documents in order, as I will move to a new apartment in November.” You could also say get/put the contract in order, either way.

That’s a perfect example. That sounds like you’re referring to the stage in a theater. It would also be common to say, “who work behind the scenes”. That would cover people who do things like lighting and sound, who are not visible but are not specifically behind the curtains.

That’s good. I would just say that “I get a lot of messages about my job” means that the topic of the message is your job (i.e. your arrangement there), not the content of your work. So if people are writing to you asking you about your job, they would be saying, “Do you like your job?” or “How long have you been at your job?”

If people are writing to you about the content of your work, you would say, “All day at work, I get a lot of emails and text messages.” You could also say, “I get work-related emails and text messages all day.” That would specify that the subject of the messages is the content of your work (not your employment arrangement).

That can work. If you mean that you’re trying to get organized, you can also say, “I’m trying to get my English activities in order” (so that I can be more effective in my studying, etc)