The phrase "dost level best" is an archaic way of saying "you are trying your hardest". The spelling of "dost" reflects its older English origin and is pronounced as /dʌst/. The word "level" is spelled as it is pronounced and is articulated as /ˈlɛvəl/. "Best" is a common word and its pronunciation is /bɛst/. This phrase is rarely used today, but it is still occasionally seen in literary works to add a touch of old-world charm.