But this year I'd like to invest some USD ... and have a guaranteed ROI after a few months.
Guaranteed? There are no guarantees, except of death. And even that's not guaranteed if you know the Lord.
I have joined those who believe that the stock market we continue to boom until all major world economies suddenly crash this year or next or possibly as late as 2020. Until the crash, the stock market should be very rewarding.
If you want to take advantage of the stock market boom, you should open an online stock brokerage account. If you don't have a favorite, you can pick one from
this list or from
this list.
Picking stocks that will give a return is difficult, but it's just as easy to buy an Exchange Traded Fund (ETF) as a stock, and they're generally safer since they spread the risk across a number of stocks. (Brokers that trade stocks also trade ETFs.) If you don't know what else to pick, pick an ETF that tracks the S&P 500 index like IVV, SPY or VOO. (Those are the stock symbols for some ETFs.)
But the other half of the belief is that after the crash, physical gold and silver will greatly increase in value. So you might consider buying some gold and silver bullion, like American Eagle coins. Many say that's not an
investment because it just sits there and doesn't return anything. But in the past, precious metals have retained value when paper currencies crashed.