That's not how you'd say it in English. You'd say The guard does not admit to being lazy. I don't know if this is one of the acceptable choices.
Nothing wrong with your Klingon. A tiny nuance in English. With that structure, one says The guard does not admit to being lazy, which I have just adjusted it to accept.
I sometimes feel badly that Duolingo marks things wrong when people use imperfect English, but then I think to myself that it's probably of more use in the long run for them to perfect their English than to learn Klingon, so I just hope they're not too frustrated as they do both at once.
Being or not to being that is the question. Mean thing when English is not your native language: You have a blind spot there sometimes. That can more easily be overcome / circumvented in other languages (dictionaries www babelfish) than in a not quite so popular language as Klingon. As I tend to be very convinced my Engish to beeing perfect, I spent some time to look for my lack in the Klingon grammar. So your comment is very helpfull. Will accept that my English is to blame and walk on! taH pagh taHbe'! (Waiting for the day when Klingon will be more popular than English ;))
We Klingon speakers are both lucky and unlucky, because native Klingon speakers never show up to tell us what we're doing wrong.
No native speakers showing up here ? You are sure about this?? Recently watched a documentation on Netflix Star Trek: DIscovery. The docu even was subtitled in Klingon! For whom would Netflix do this, if there weren't no warriors on this planet??? Who did write this beautiful piece of literature that got translated in many terran languages: Qo'noS ta'puq, Hamlet lotlut???? There is an easy answer to this, think about it.