Students should note that HISlaH, qaH or HIja', qaH can only be used to answer a yes/no question. If you are ordered to do something, the correct response is lu', qaH or luq, qaH, which mean Yes, sir in the sense of okay, sir, I'll do that
It doesn't necessarily imply respect. Calling someone qaH or sir just shows acknowledgement of the addressee's superior station.
It's also more than just agreement. It's an answer to a yes/no question. If your superior told you, Ha'! matlhutlhnIS Come on! We need to drink, you wouldn't agree by saying HISlaH, qaH; you'd say lu', qaH Okay, sir.*
Note also that qaH is gender-neutral, while sir is usually masculine. Whereas in English we might address a woman as madam or ma'am instead of sir, in Klingon she is still qaH. I wonder if this course considers that possibility?