I wanted to see how can you notice if you need new or either service them by putting fluid?
Im not sure on this so if I sound dumb , I need your help?

 

If your forks are leaking, you need to rebuild them with new seals.
- Wetness on front brakes
- Puddle on ground after it sits a while
- Puddle on wheel rim after it sits a while
- Wetness on dust guards at middle of fork
- Slick, slippery oil on upper fork tube itself
- Evidence of surface rust on upper fork tube will often lead to damaged fork seals - and leaks

If your forks are bent from an accident, you need to replace them.

 

+1 I concur!

 

That list pretty much covers everything, haha.

I had to replace mine recently, after looking down at a red light and seeing a good bit of fluid leaking from the right fork.