which parts of c# and .net should i learn for ninjascript? and which ones to skip?
am not coder i just started learning c#

Try this to get started.
There are other resources not on the NT web. Simplest thing is to do a web search or youtube.

https://support.ninjatrader.com/s/article/Developer-Guide-Getting-Started-with-NinjaScript?language=en_US

Try building something simple on Ninja Script Builder, and when you have script working you can open it w builder and open up to look into it and see how things work and build on what you know from there.