shower
The French word 'douche' is used to refer to a shower, which is a device for bathing where water is sprayed onto the body from a showerhead. In French, it can also refer to the act of showering, similar to the English usage. For example, one might say 'Je prends une douche' to express 'I am taking a shower'.
I'm going to take a shower.
This phrase is a common way to express intention of taking a shower. 'Vais' is the first person singular form of the verb 'aller' (to go), often used to express near future.
The shower is broken.
This phrase is used to state that something, in this case the shower, is broken or not working. 'Est' is the third person singular form of 'être' (to be) and 'cassée' is the feminine form of 'cassé' (broken).
The bathroom has a shower.
This phrase is used to describe what is present in a location, in this case, the bathroom. 'A' is the third person singular form of 'avoir' (to have).