Hi abdoe7,
If you click the "Oplossen" button, it will not remove the add-on, but will instead open your Avast Antivirus application to show you which add-on is causing the issue (see the attached screenshot for the screen shown in English).
I have tested the add-ons you mentioned, and it seems that it is the "Outlook Web Enhancement" add-on that has the bad reputation. I have reported this to the relevant team now to check whether the warning is correct.
BCU in this case stands for Browser Clean Up
This is the part of the Antivirus application that is detecting the add-on.