it depends on what kinda design you like - contemporary designs, traditional designs etc.
Once you know that designing what you want becomes easy.
Walls - you can have all white walls and one different colour wall.
Sofa - This is the center of your living room and other designs and colour revolve around it. Pick sleek, sold colour sofas.
A center table that goes along with the sofa and a big carpet under it.
Curtain - curtain colours should match the sofa.
Pick one spot for the study table, its placement doesn't look good.

Study table isnt supposed to be there, it will be out. It’s there due to this lockdown as a makeshift study room kinda thing. I’d like something minimal and light colored. All this furniture is around 20 years old. Can you suggest some color palettes please.

You can have white walls with dark blue/green 3 seater sofa and contrasting one seaters, silver/grey/beige color curtains.
More lighter colours you use, bigger the room looks.
Most Indias think twice before buying white furniture but honestly it looks good in any room.

Thank you, i do agree white looks great. Can I use wallpaper on any of the wall? And if yes then any tips for choosing the right color. Also, I wanted a false ceiling, what kind would look nice ?