Complex sentence: In the middle of 1967, she was replaced by a lighthouse, at which point she returned to serving as a Reserve-Lightvessel mainly in the North Sea under the name "Kiel", and afterwards as a permanent replacement for the retired "Amrumbank".
Split into simpler sentences: In the middle of 1967, she was replaced by a lighthouse. After that, she returned to serving as a Reserve-Lightvessle, but now under the name "Kiel", mainly in the North Sea, and afterwards as a permanent replacement for the retired "Amrumbank".