Hi New Guy,
Since you're 19, and 75kg's and 5'7 tall, with reasonably good paddle fitness and wave knowledge, and by the sounds of it, reasonable flexibility....
I would lean towards either of these;
NSP 6'8 Fun Board (7'2 might be OK too, but at your height, the 6'8 should be OK)
NSP 6'4 Fish has some potential
NSP 6'6 Shortboard could be OK.
Maurice Cole in 6'6 or 6'8 - these boards are glassed reasonably well, mid weight (not ultra light, light thin, and ultra weak). I'll duck into Rip Curl Torquay tomorrow to take a closer look if I remember. But it appears to have a slightly fuller nose template, and those little hips at the rear fins. Both of these features are good for learning.
Obviously fuller templates, and bigger board areas, and flatter rockers help your paddle in speed, and overall paddle speeds.
Also,
watch plenty of surfing videos/dvd's/movies/youtube clips. Also watch some of the older school stuff from the 70's, for clean "no frills" surfing, for just getting the basics right. Watch closely how they perform the bottom turns, and cutbacks, and when they do the leg extensions and compressions, which is powering for speed (as opposed to 'pumping' for speed / bunny hops). And watch and think how the ankles and hips are working with the knees.... it all comes fairly naturally though...
Are you goofy or natural ? WA is the goofy footers playground ! So is Indo. If I was goofy I would marry an Indonesian girl, and live there !! But I'm a natural footer, and have the Torquay Points as the playground! But I should do more work on my backhand!
Even try body boarding, or surf mat riding. When there is swell, but if conditions are ugly, a surf mat will still help you feel the power of the waves, and help you timing... Even just when dropping in on a mat, think about when you would get to your feet, etc. It's all fun !! You don't have to surf a 5'11 pro model to have a blast !!