Yes; with AutoFX enabled, your funds will be automatically converted when you trade in another currency. When this conversion happens, you are charged the AutoFX fee.
The AutoFX fee is 0.25% of the amount converted.
Alternatively, you can enable manual currency handling, and convert a lump sum manually to trade with. The fee for a manual currency conversion is 10.00€ + 0.25% of the amount converted.
When a currency conversion occurs on your account, you will see the entries FX Credit and FX Withdrawal in your Account Statement. These entries are not fees, rather how the foreign currency transaction is booked in your base currency.