I was tricked into installing a fake new version of my Electrum wallet. The message arrived as an error message for my attempted transaction and said that I need to install electrum 4.0 version in order to make the transaction, which I can download from electrumbox.com. So I did... And unknowingly installed a the fake wallet mirror app, which as soon as I had my passwords input, switched the delivery address and the amount (to the full wallet balance) and transferred all my bitcoins to this address, thereby stealing them.