Did you check How do I know if its working? section and check the realtime graph whether it moves like that?  I think EU game servers for Black Desert is already supported by Mudfish.

i see Europe(Netherlands) on the node list for black desert. its the closest location to the EU server in France. and it has increased my ping from 250+(normal) to 370+(Mudfish).

Did you try to change a mudfish node based on FAQ - Nodes section for your game item? If you're using the advanced mode, please start with the basic mode.