Can't delete partition

Hi,

I tried to create a partition to be able to boot into Linux on my MBP (2013).
I do not intend to use it anymore so I want to delete it.
The normal way of doing it does not seem to work for me. It is greyed out.
Formatting the partition to a different format does not work. I hit apply, it shows a loading bar for a fraction of a second. When I want to quit disk utility it warns me that the changes have not been applied yet. This also fails to work in recovery mode.
There are multiple other people online who seem to have this problem. but their solutions don't work for me.

What do I do to solve this issue?
Kamik423