You can withdraw funds from your DEGIRO account back to your primary registered bank account by clicking on Deposit/Withdraw funds in the right upper corner of the trading platform. In the app you can find this section by clicking on the menu in the left upper corner and then choosing "Deposit/Withdraw". On the Czech platform, withdrawals are possible only in CZK. Hence, you will need to use a tool for manual conversion (fees are waived) and convert EUR to CZK.
You cannot withdraw funds which are currently invested. Withdrawals take up to 2-4 working days to be completed