Hello OJFord, the feedback is not to be provided here. But with the report button only.
As here, it's reserved for grammar tips, questions, helps. And they won't read everything to know what can be improved, it would be too much work. So, the report button was made, to be the only way to add suggestions.
So, your feedback part is not at the right place, but your question about "is it good grammar" is at the right place here.
I personally feel as though "not sleeping" is more natural, but yeah, I'd say give them some leeway at first. The course is still in its very early beta stage, not even released half a day ago yet, so they haven't had much time, if any, to correct any mistakes that have been reported yet. Just give it some time c:
"Marcus is writing and not sleeping" should be accepted because it is grammatically correct, idiomatic English.
The course is new. It's going to be missing a lot of options in English.
You should use the report button to flag missing translations, word order errors, etc., when you're certain, or at least nearly certain. But be careful to look for typos first.
The Latin team has been very good about improving the database based on user suggestions. The process behind the scenes can be slow, we've been told.
Here's a complete guide on what to report and what not to report, specific to the new Latin course: