Kaiser Wilhelm II (the last German Emperor) visits some troops in the field during World War I. He appears to be chastising one man for replacing his spiked helmet with a fruit bowl.
The pointed helmet is called a Pickelhaube (plural Pickelhauben; from the old German Pickel = “point” or “pickaxe”, and Haube = “bonnet”, a general word for headgear). They were originally made of boiled leather, but later thin sheet steel was used.
By 1916 the design was proven ineffective for trench warfare and abandoned. It was replaced with the Stahlhelm – the German helmet you think of when you think of Germen helmets.
The helmet with the flat top? I have no idea what that thing is, but it looks upside down.