You’ve already had 2 or 3 sessions and you notice that when you manage to place your feet correctly, you advance a few meters even with your bad pumping. It’s time to start improving that pumping.
If you skate, you’ll understand this easily, since a very similar movement is done to gain speed on descents and not lose it on climbs. In this way, you can ride forever without touching the ground with your foot.
When you start an uphill, you bend your legs a little and push yourself up a little (without jumping) to take weight off the board and thus prevent it from slowing down on the climb. When the slope goes down, you also bend your legs a little, but just the opposite way, to put pressure on the board and thus gain speed.
When you go uphill and downhill, the pressure on the board to give it speed on the descent is also used to propel you upwards and take weight off the board and make it go up the slope with less resistance. This is very similar to what is done in pumpfoil, by giving weight to the board we gain speed and by taking it off we gain height.
Practice it like this for a couple of sessions without going crazy with more things, record yourself on video and see if you bend your knees and if you fully stretch them again.
Forget about your arms for the moment, let them move freely wherever they want, right now they are a tool to help you maintain balance, not to help you pump.
Here you have to start looking ahead, but don’t look at the horizon, but a few meters ahead of you like when you’re riding a bike and you look a few meters ahead seeing if there’s something on the road, but with the corner of your eye you still have the reference of the tip of the board.