Hello !
At first try to do some tutorials even if they aren’t related to your actual project. What matter the most is learning the tools and the logic of GN.
GN is really a different way to interact with 3D geometry, it’s still 3D but it’s a new universe on it’s own, so act if you were learning 3D again.
I’d recommend to focus on learning the system first, and exercise yourself to solve simple problems, like how to resize a curve, how to extrude. You need to learn to deconstruct modeling process into simple nodes operation ( given available node set) …
Once you have good basics it will be much simpler to work on your actual project, since it’s just an accumulation of problems to solve, or how to chain different operation using nodes.
Beginners mistake I see is to jump too soon on real life projects, without good basics it’s very easy to fail hard…
You can have a look here for tutorials and resources : Let's regroup Geometry Nodes Groups - Resources and Links