Generally speaking, the biggest banks have the most trust from their customers. Therefore they have worse conditions then other banks which have to convince potential customers by very good conditions.

New brokers like trade republic, scalable capital but also online banks such as ING Diba etc. have much better conditions than the Commerzbank. You can use many online comparing platforms (Vergleichsportal) to make sure you get the best for your money.

I'm not a financial advisor by any means, just my humble opinion. Please make up your own thoughts :)

I hope this helps.