It is my first time to hear about tradenix. I think you don't have to choose them as the exchange because I think that site is new, and we don't know how good their reputations. Maybe you can try to visit binance because binance is a big exchange, and I know that many people here are trading on that site. We have another big exchange like poloniex, bittrex, kucoin, and else so you can try to look at it. I recommend those sites I mention, but binance still favored by most people here.
Same here, I've never heard about that so far. The key is to find trustworthy crypto exchange e.g. like these above, so there would be nothing to worry about. Do extensive research about them and choose wisely.
This is fishing! Some guy said something and you need to believe him with your money? Scammers are ready to do literally anything to draw your attention and persuade you to invest some money. Don't buy that shit, any honest guy will not ask you for money, and he will not promise you anything big.
Beginner trader should spend some time reading about trading, to see what exchanges are the best and simply to jump in, you will learn to swim after some time. Check exchange, look what is what, check forums for everything unfamiliar, and with time you will get knowledge and experience! Good luck to all beginners!