"Dost with" is an archaic phrase that means "finished with" or "done with." There are plenty of other synonyms that you can use instead of this old-fashioned phrase. Some of the words you can use as a substitute for "dost with" include completed, concluded, finished, terminated, and ended. Other options include over, through, fulfilled, accomplished, wrapped up, and closed. No matter which synonym you choose, make sure that it is appropriate for the tone and context of your writing and that it accurately conveys the intended meaning. Choosing the right words can make a big difference in how your writing is received.