ok, few things. firstly - bend you knees, that ironleg stance is a common thing with beginners, you can stamp weight down like that but you need to unweight the board as it comes back up the wave and you cant do that without compressing and then decompressing from the knees.
secondly you need to pump higher up the wave not on the flats so you needed to take off at more of angle to the beach and stay high on a small wave like that. on that wave you should have been on that first section which came down in front of you not heading out in front of it, then it would have given you a boost out to towards the shoulder and set you up for the wave. by trying to drop in and go round it you stalled on the flats and the wave was basically over from there.
you could have taken off earlier if you where paddling a bit quicker too, that would have helped give you a bit more time.
also you need to pump rail to rail up and down the wave rather than just hopping up and down in a straight line, its basically accentuating the drop down the face and minimising the force of gravity as you come back up the face by unweighting which builds your speed.
if you have an old style bathroom scales (non-digital) you can stand on them and practice weighting and unweighting from the knees on them and see the results as the needle goes from above your normal weight to almost zero when you unweight.
sorry im not very good at explaining this type of thing but i hope that helps, when you get it right once youll know it feels different (less forced and more natural)