Hello,
A vast majority of my portfolio is of US stocks alone. Apart from FX risk, is there anything that i should be aware of when I use trading212?
Also would taking some money out every once in a while, a problem? (Hidden fees, taxes etc.)
P.S. : I live in Germany. So my currency is €
Cheers 
Mainly it’s just the FX fees to be aware of. So if possible take money when it’s at a favorable rate.
You will always get sector risk, of whichever stock sectors you have chosen to go into.
Sometimes there is a tiny fee of roughly 0.01 applied which is a FINRA fee, but this is nothing to worry about.
Other than that, I can’t think of anything else which would affect you much.