Hi Bribed and der_meister. The Error 520 is a connectivity issue. Our developers are working towards a solution, but as of right now this can still happen intermittently.
The issue where you see that you need a higher Tier in order to deposit/withdraw is actually a trading engine issue. We were launching the trading engine on the 6th but ran into some obstacles. You can read more about this
here. For the time being, we would suggest waiting a moment and refreshing the page.
Thanks for the answer! So normally it should work as I understand. I tried to refresh the page several times already but always got the same situation. I logged off for now and have to go anyways. Will try it again tonight. Hopefully it will work out then!