I got a bitcoin coupon as a gift. I got the bitcoins into my wallet (Bread). Now I would like to transfer those coins into a market place like eToro or similar to start by selling some of them. I haven't found a way how to do that so far. Any help would be very welcome.
Marketplaces (as well as ATM's for this matter) typically require you to send the bitcoins to an address of theirs. As soon as that transaction confirms, they send you cash via a traditional bank account, paypal etc...
Any trustworthy marketplace will describe that process in detail. Here is some information from btcdirect, for example: https://btcdirect.eu/en-ie/purchase-order