What is shown adjacent to the (Apple) in the Mac's menu bar?
If it is DuckDuckGo then the Dock's settings got messed up. Not a problem, just return to the Finder, launch Safari from Applications (Go menu > Applications), find the new Safari icon in the Dock, and drag it to where you want it to remain in the Dock.
Return to the DuckDuckGo app and quit the app. Drag that one's icon up, out, or away, a sufficient distance from the Dock until Remove appears. Let it go.
If you want DuckDuckGo to remain in the Dock, find it in Applications the same way, and repeat the above. It should resemble the DuckDuckGo app icon shown in Applications. If it does not, you'll need some more challenging instructions.
Refer to Use the Dock on Mac - Apple Support.