It is not a problem, it's simply a "beta" course. That means that the course is still unstable, buggy and alternative translations are missing. If the course members had added each possible translation for each sentence, this course wouldn't have been released before 2017 or 2018, believe me. "It is orange, right?" is fine and should be reported (I'm a mod, but no member of the team, thus I cannot add it in the incubator directly).
In any course, beta or not, you can be click the "report a problem" button, or the little flag (mobile) to suggest another translation. If they accept your translation, eventually you'll get an email saying so. (I sometimes get a whole batch of emails when someone goes through and clears the backlog.)
Because the first part is not a question, it's a statement. Esperanto, like English, has what's called a tag question. It's where you take a statement and then tag a mini question at the end.
It is orange, [statement] isn't it? [question]
Gxi estas orangxkolora, [statement] cxu ne? [question]
This is not the same thing as "Is it orange or not?"/"Cxu gxi estas orangxkolora aux ne?"
As long as it accepts x-notation and merely flags it as a typo, rather than marking it as fully wrong, I wouldn't worry about it.
I use a program called Phrase Express. It's relatively easy to set up (although it can get painstaking depending on how many entries you want to add) but once it's set up you can just let it work in the background.
So I have it set up to (among other things) convert x-notation to diacritics. I type, say,
gx and hit space, and it gives me the option to convert that to
ĝ by hitting tab.
"It isn't" is equivalent to "it is not", but that's not what's needed here.
"It is not/It isn't" is a simple statement.
"Is it not?/Isn't it?" is a tag question that goes after a positive question.
If the question were negative, for example "It's not orange?" then the tag question would be the positive "is it?"