Steglitz-Zehlendorf rentals with pool

We booked this apartment at short notice when our original Home Away booking made 6 months in advance was cancelled 3 days out due to a building issue. The booking requires an upfront payment on booking request. Once accepted we were advised to download an app from a link that we did not receive, apparently due to our Australian account? Unfortunately, this left us without what I assume would have been essential and useful information regarding the apartment and the neighbourhood. An alternative link was sent but it provided information in German which was lost on us. The apartment is spacious, well appointed, comfortable. The bedrooms are not ensuited and both bathrooms are located at one end of the apartment. On arrival we were met, given a brief overview and paid our security deposit and city tax in cash. The owners made it clear that were available and accessible. Like most travellers we prefer to be as independent as possible. Our concerns are that if the app is not accessible to everyone an old fashioned information sheet in the apartment is a necessity. Secondly, the owners withheld credit card fees from our security deposit. When the only payment method is via Home Away these charges are unavoidable and should be upfront and factored into the costing. A security deposit is a purpose fit payment and should not be a means of garnering further revenue. The location is good, the apartment is good, our experience was less than ideal.