Beginner question: Fund managing companies good?

I am a beginner in this and one of the friends mentioned a fund management company. Got their brochure where they say…

▪ Total Absolute returns: 91%
▪ Annualized returns: 34%

They take 20% of the profit share. No other fees.

As a beginner, it looks like a no-brainer. So, what’s the catch? Why should I do it myself instead of going with this firm? What am I missing?