Should I invest in S&P500 or through a Robo-advisor for passive investment?

You could do it stand alone for sure, you could also just start and try, f.ex.

50% stand alone

50% Robo

somethings:

-stay put a least 5-10 years with both methods, NEVER, never panic and sell on big crashes, never, when you selection of ETFs was sound in the first place

-read a lot about passive investing and aggressive reduction of ANY fees (broker, taxes, ETF annual total expense ratio = TER)

-for Your choice ticker VUSA would be an obvious selection

• also consider for better diversification an MSCI World or MSCI World ex-USA UCITS ETF

some ideas (but some of them riskier, be cautious !) here:

https://seedly.sg/questions/what-is-your-genera...

GOOD LUCK, all will go fine !