Firstly You're not "investing" - You're betting.
Now currency exchange rates are based in real life trade neccesities between countries and therefore are stuck within certain limits, but can go up or down. It is up to you to choose the correct direction timing and exits.
"Crypto" is pure speculation. It can go "to the moon" - it can go to zero. - choose whichever your appetite for risk dictates.
Forex will need you to learn a lot and it will be hard and you can still go bust.
Crypto - will either make you a lot of money, or it will bust you. ! Little skill and simple coin flip like betting red/black in Roulette.