I thought the nether was gonna work with the same shader files from the overworld but when I went through the portal, I saw a different story. Everything looked dark, dark as if it was nighttime during overworld but with no moon, also realised that the entities had a transparent body. So these 2 issues were fixed along with the nether shader base when I made it. Things that were done are:

• Fixed nether lighting
• Added shadows
• Removed fog codes from composite.fsh
  What I have noticed was that I got slight better fps in nether than overworld cuz lots of parts of nether consist of wasteland biome which has less structures and vegetation.