Answer
DEGIRO immediately exchanges (on an continuous basis) the money that you transfer to one of the Money Market Funds. The Money Market Funds are investment funds that aim, with as little risk as possible, to achieve a yield that is slightly below the regular market rate in the currency concerned. For more information concerning the investments in the Money Market Funds you can click here.
All assets within the Money Market Funds are held separately by an independent legal entity and therefor does not run any risk in the event of bankruptcy of DEGIRO or or flatexDEGIRO Bank AG.