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You can only log in once at a time on a download server. If you want to download a lot of files at the same time file faster, use bittorrent :)
Important : This file URL is unique for you, if you want to link to this download, you will have to use: https://www.gamersyde.com/video_the_witcher_3_wild_hunt_microsoft_conference_demo_lq_-32264_en.html