I-485 question 15 , 18 - what should I say ? and also should I attach my military certificate of service?

I served military service ( It is mandatory in my country) I attend the first 2 month in military ( tutorial period) but I pass the rest as a researcher in an organisation. (it is an option for any one who can find somewhere out of the military for service) I think I have to say yes to both questions 15 and 18 but please make me sure: Should I explain it in the continuation sheet? If so, should I attach the translation of my military certificate service? I have a certificate from the organization that I worked for them as my military service that shows the dates but it hasn't mentioned that it was served as my military service. Thank you.