This guide is based on wikipedia's list of birds of Germany with accidentals removed to keep the guide under 500 entries.
The River Warbler (Locustella fluviatilis) is an Old World warbler in the grass warbler genus Locustella. It breeds in east and central Europe into western Asia. It is migratory, wintering in east Africa.
The Savi's Warbler (Locustella luscinioides) is a species of Old World warbler in the grass warbler genus Locustella. It breeds in southern Europe and temperate western Asia. It is migratory, wintering in northern and sub-Saharan Africa.
The Common Grasshopper Warbler (Locustella naevia) is a species of Old World warbler in the grass warbler genus Locustella. It breeds across much of temperate Europe and western Asia. It is migratory, wintering in north and west Africa.