In what ways does Gawain represent a flat/static character? Or in what ways does he represent a round/dynamic character?

The protagonist of the poem, Sir Gawain is the central figure whose fundamental character change forms the focus of the work. At the start of the poem he is an eager, optimistic, and loyal knight who undertakes the Green Knight's challenge to protect Arthur and preserve the reputation of Camelot. By the end, he has come to question the viability of the chivalric code and realize the weakness in his own human nature. Ultimately, it is his instinctive fear of mortality which comes in conflict the societal values he has learned ­ and it is this conflict which leaves Gawain feeling troubled at the poem's close. You can check more out below:

http://www.gradesaver.com/sir-gawain-and-the-green-knight/study-guide/character-list