Apt-get error help

I’ve been trying to update my apt since yesterday but its not working. I get this error every time:
The repository ‘http://obs-master.endlessm-sf.com:82/shared/eos eos3.3 Release’ does not have a Release file.
N: Data from such a repository can’t be authenticated and is therefore potentially dangerous to use.
N: See apt-secure(8) manpage for repository creation and user configuration details.
E: Failed to fetch http://obs-master.endlessm-sf.com:82/shared/eos/dists/eos3.3/core/source/Sources 500 Internal Server Error
E: Some index files failed to download. They have been ignored, or old ones used instead.
How can I fix this problem?

@LICCMAPP To upgrade to the latest Endless OS version just go to the App Center