Fixing dangles (lines) with v.clean and "fix geometries"

I need help with fixing my two dangle-errors:

there are 2 dangles on the top right and one small hole on the top-left corner.

I can deduct them with the Geometry Checker, but I cannot fix it (automatically).

This is only an example-file. I need the skill for a big file with hundreds of lines that need fixing before polygonizing…

Has someone an idea why v.clean (I ticked line and break, snap, rmdangle with tresholds 0,5,5) or geometry fixer cannot do that?

I already studied useful information like that:

• https://www.geodose.com/2017/10/how-to-clean-topology-error-in-qgis.html
• https://www.geodose.com/2017/09/how-to-check-topology-error-in-qgis.html
• Finding Invalid Geometry using QGIS?
• https://www.qgistutorials.com/en/docs/3/handling_invalid_geometries.html
• What am I doing wrong with QGIS v.clean?
• https://www.qgistutorials.com/en/docs/3/handling_invalid_geometries.html

… but still it is not working.