Missing Release file in Debian repository

[CasperNielsen]

Getting this error when trying to update repository. After adding "deb https://www.mindforger.com/debian stretch main" to the /etc/apt/sources.list.

E: The repository 'https://www.mindforger.com/debian stretch Release' does not have a Release file. N: Updating from such a repository can't be done securely, and is therefore disabled by default. N: See apt-secure(8) manpage for repository creation and user configuration details.