The instructor really knows the subject.
The sentence is referring to a instructor so it should be the instructor not that instructor. It shouldn't be written as reallyknows it should be really knows. There is no need to capitalise the first alphabet of subject as it is simply a common noun.
To know more about "grammar and editing" refer to the link here:brainly.com/question/49114646
You put the comma here: Ricky has a job, but Wanda is unemployment.
Hope helps!-Aparri
