to understand; to know; to comprehend

to grow beyond the naivete of childhood; to be aware of what is going on in the world; (esp. of a child) sensible; thoughtful; intelligent

(slang) Mr. Know-it-all

to be savvy

(coll.) to know the ropes; an expert

unable to make sense of what one is hearing

to understand (on hearing); to catch (what is spoken)

unable to make sense of (sth)

unable to make sense of what one is looking at

to understand (by hearing); to catch (what sb says)