Update Opengist.sh: Fix broken backup function

[bvdberg01]

✍️ Description

After installing Opengist I found a problem with the update script.
This PR contains the following:

• Fixes only that the service stops when there is an update available.
• Backups the config file and puts it back on the correct place
• Website JSON updateable true

✅ Prerequisites

The following steps must be completed for the pull request to be considered:

• Self-review performed (I have reviewed my code to ensure it follows established patterns and conventions.)
• Testing performed (I have thoroughly tested my changes and verified expected functionality.)

🛠️ Type of Change

Please check the relevant options:

• Bug fix (non-breaking change that resolves an issue)
• [] New feature (non-breaking change that adds functionality)
• [] Breaking change (fix or feature that would cause existing functionality to change unexpectedly)
• [] New script (a fully functional and thoroughly tested script or set of scripts)

[MickLesk]

Can you change/modify the title to harmonize for Changelog?