You can easily decide yourself whether your activities should be visible or not. You can change the settings directly in the app.
Click on your picture/name abbreviation in the upper left corner of the app. Now select Settings and then the overview point Private.
Here you can use a slider to select whether your profile is public or not.
Alternatively you can use this link. If you don't want to be displayed anymore, uncheck the box Show profile in search and public lists.