the recommended way is to use backups to setup multi-device. (transfers existing messages, chats, encryption keys, contacts and so on.)
We’re planing to make backup transfer easier (transfer the backup encrypted over local network initiated by an qr code scan).
We didn’t bought an certificate yet, so the builds are unsigned and windows defender seems to block everything unsigned. Why didn’t you download it though the store app? if you’re on win10, you might as well use it: https://www.microsoft.com/en-us/p/deltachat/9pjtxx7hn3pk?activetab=pivot:overviewtab
related: Windows Defender reports malware