Add to the tea pot the green tea leaves with little boiling water, mix it a bit and throw out this first water. That will help in removing the bitterness of the grean tea.
Now add to the teapot with the green tea, the mint leaves, the water and sugar. See that the mint leaves are properly submerged, or you might get a bit of a burned bitter taste.
Never mix with a spoon the content in the tea pot. Morrocans use a small glass inside the tea pot to mix it properly. Cook it for 5 minutes, but not any longer, or it will get too bitter and serve it hot. enjoy!