Are you looking for the adjustment brush (Korrekturpinsel) like you wrote in the title, or for the healing brush (Reparaturpinsel) like you say in the message? The healing brush is where @Ian Lyons shows you, the adjustment brush is part of the new masking tools now, so you get there by clicking on the right most icon.
Your screenshot is for Lightroom Classic, which isn't the cloud version of Lightroom, and may explain why the 'Heal' tool button isn't where you expect to see it.
In Lightroom Classic, the Heal tool (repair brush) is the middle button in your screenshot.
AdChoices