Hi Coop,
yes, if Sparkasse has increased their fees within the last years, you could reimburse the difference with the sample letter from the linked website, because you didn't actively agree to the terms.
The BGH had ruled on 27 April 2021 that if a bank’s general terms and conditions deemed the customer’s consent to changes to the terms and conditions to have been given, without any restrictions as to the content of such changes, and thus also to changes to fees, such terms were invalid.
Do you want to switch banking accounts? From Sparkasse to Commerzbank? Or could you give more information about your second question?
Have a nice evening.
All the best,
Anita