What were the disadvantages of using Machine gun in world war 1?

Ive recently learnt about the machine gun in my history class and here is the main disadvantage but there were also a lot of advantages too.

for instance the machine gun often over heated which caused a big problem because they weren't able to use them until they cooled back down.

to cool them back down they usually put them in water but this could be a big problem if there weren't any water around.