Hi there Discoja, if you look at the catch on the bonnet lid, the one with a spring on it, you will see a slot cut into the end of it to fit a flat-bladed screwdriver. At the top end of the catch is a locking nut.
Undo the locking nut and turn the catch anti-clockwise with a screwdriver one full turn, then drop the bonnet to close it and decide if that has improved it sufficiently.
Play with settings until you are happy.
Good luck
Dave