Best places to stay and visit

Hey guys, I'm coming to Delhi for 3-4 days towards the end of the month for an exam. My exam will last around 2 hours in Safdarjung after which I have plenty of time.

What are some good areas to stay which are closer to the famous spots in Delhi? I will be leaving by train, so something which can easily get me to the station would be nice.

I've been to Delhi 8-9 years ago with my Mom and I saw a lot of cool stuff like Delhi Hasr, India Gate, Rashtrapati Bavan, National Museum, CP, Kingdom of Dreams, etc.

I'd love to know you recommendations on spots to visit and shopping/thrifting areas. Also, what things should I keep in mind as a solo traveler to your beautiful city?

Thank you:)