A placed order can be cancelled free of charge under "Transactions" if it has not yet been fully executed. A direct modification of an order is not possible. If you want to change an order that has not yet been executed, cancel it and set it again.
You can find information on trading hours and therefore also on restrictions on cancelations here: What are the trading hours of the European Investor Exchange, gettex and Xetra?
According to the Conditions for Transactions on the Munich Stock Exchange (IV. Section), trades can be cancelled retroactively by the exchange under certain conditions. This applies in particular to so-called mistrades. Mistrades can, for example, be caused by technical malfunctions or an obviously deviating reference price. In the event of a cancellation of your already executed order, you will be informed by e-mail. Limit or stop orders will not be reactivated. Therefore, if necessary, please place the corresponding order again.
According to the Conditions for Transactions on the Munich Stock Exchange (IV. Section), trades can be cancelled retroactively by the exchange under certain conditions. This applies in particular to so-called mistrades. Mistrades can, for example, be caused by technical malfunctions or an obviously deviating reference price. In the event of a cancellation of your already executed order, you will be informed by e-mail. Limit or stop orders will not be reactivated. Therefore, if necessary, please place the corresponding order again.
Similarly, corrections due to mistrades can also be made for trading orders on the European Investor Exchange. See Mistrade Rule §35 of the Exchange Rules of the Lower Saxony Stock Exchange in Hanover.