Shall I sell my investments in mutual funds and buy gold?

That is a very broad question.

If that investment is going for retirement then don't go for gold. It really depends on your age and your knowledge in investment. If you are not too familiar with investment, finance, analysis then don't go over your head because you will regret it. Even if you win it is just similar as guessing.

Perhaps if you are unhappy with your mutual fund performance you can switch your provider or make changes to your mutual fund.