Why can’t I build originals

I’ve had this trouble ever since I started playing and used a tutorial. I could follow the most complex tutorial fine and if it went wrong I could fix it fine by myself. If somebody’s build is wrong or not working I know exactly how to fix it (most of the time) and it would work. But since I’ve started training to be a pilot I’ve been wanting to build some aircraft I fly and also the glider I own.

I’m massively into gliders so if course I found a tutorial for one. It wasn’t bad but I modified it into an LS4 which turned out alright. I’ve been wanting to make my own glider after doing this which is a Ka6-CR, it’s has so many curves and the skid is just impossible. I am now looking at a Duo Discus which I have also flown and I would like to build plus it is similar to the tutorial glider I modified. But of course I can’t even do that for some reason…

I understand everything but I just can’t use that to build something. Does anybody have any tips because I would love to make these and do them accurately🙏
Any help is appreciated thanks!