What’s the best mutual fund I can invest in?

No one can predict how a mutual fund would perform in the long run. Data also shows consistently chasing best mutual funds result in behavior gap. Pick one that you can stay with for long term.
If you google top mutual funds, you'd find plenty of communities or online publications tossing you some names of well performing funds.
No one can predict how markets would perform in near future (short term), or over long periods of time. And when we say no one, we really mean no one at all.
Amsterdam is the oldest stock exchange, founded in the 1460s. London stock exchange is one of the oldest, founded in 1801, with nearly ~220 years of history. US markets have been around for ~200+ years, since the early 1800s (NYSE was established in 1817). Indian markets are relatively young, been around for only a little over 40 years, in any meaningful way. BSE was founded in 1870s, but it's hard to find reliable data since before Sensex was created in 1979. Some even suggest to ignore data from before NSE was created in 1994, which gives us ~25 years worth of market data to analyse.
Despite all these data, there's no prediction algorithm or deep-learning solutions; that can predict future market behavior accurately or near-accurately. Markets would surprise you from time-to-time, and new events would keep on happening in all markets, all over the world.
Mutual funds give you exposure to markets, and their ups & downs are linked to market's movements. It's mostly not up to the fund.
Lion's share of performance of a fund, is due to luck - just having right exposure to right assets at the right time. Very little is due to fund manager's skill in asset picking.
There are different mutual funds, that invest in different types of assets. Some invest in stocks, some buy debt, while some others bet on commodities like gold etc.
The mutual fund that's best for you, is the one that help you with reaching your financial goals. If you need a certain amount of money after a given number of years; then for that financial goal, the mutual fund that helps you get there comfortably in time, is the best option.
For most retail investors, the problem is not the right fund picking. Any average fund would be good enough for most people.
Real problem is not investing enough, and relying too much on returns to make up for the low investment amount. Or not staying with a decent fund long enough.
Asking for best mutual fund is no different from asking which gym is best for you. Finding the perfect gym is not that important. Just like it's more important to be disciplined, in achieving your health & fitness goals, it's also important in achieving your financial nirvana.
Please go through this link if you are interested in the ELI5 guide to selecting an equity mutual fund