The phrase "didst a bit" is an old-fashioned way of saying "you did a little." If you're looking for synonyms to replace this phrase, there are many options available to you. Some possible alternatives include "made a small attempt," "tried a little," "made a small effort," "gave a little effort," or "put in a bit of work." These phrases all convey the same basic idea as "didst a bit" but in a more contemporary and accessible way. Depending on the context in which you're using this phrase, you may need to adjust your wording to fit the tone and style of your writing or conversation.