understanding, comprehension / appreciation

degree, extent / level, standard / about, approximately

understand, comprehend / appreciate

question, problem on homework etc. / a question; a matter (of time etc.) / a problem (something that needs to be dealt with); a trouble / an issue; a matter

impossible to understand, utterly confused

(informal) no problem

unthinkable, out of the question

practical question (problem)

matter of life or death / (idiomatic) an extremely urgent matter

viewing as a problem