Well done everyone
try lengthening your stirrups, will make it easier to rise to the trot. There are two ways you can measure.
1/ when standing on ground put tips of fingers at buckle of stirrup leathers where they fit on to saddle, hold stirrup up to your arm pit - it should fit length of arm comfortably. Then when you are on you may want to go up or down one hole.
2/ While sitting on horse sitting straight with legs just resting down base of stirrup should sit just below ankle bone.
With the stirrups as short as you have them in the bottom pic you are trying to heave your body off the stirrups with every step. What you want to achieve is that you are rising off your knees but the horse is more or less 'throwing' you into the rise. does that make sense?
when you are working on a circle when the outside shoulder goes forward you go forward (so when that foot hits the ground you sit).
When starting out you may need to look to see which diagonal you are on but you will start to feel when you are wrong.
~Arabs are very smart and know how to conserve energy, so if you are not giving clear commands they may choose to ignore you, or decide they don't especially feel like doing anything so you have to convince them firmly that you really mean it when you ask for something