Aktivating Plugin “Service Box” has destroyed my website

Hello,
I have just installed and activated the wordpress plug-in “Service Box” in order to test it building my website. Unfortunately, directly after activating this plug-in my dashboard and the complete website was destroyed, nothing more to see on my computer/in my dashboard. Now, I have no chance to deinstall this plug-in because I do not have any access to my dashboard.
Can anyone help me with this special issue?
Thanks a lot!