museum
The word 'Museum' is used in German just like it is in English, to refer to a building or institution that houses and cares for a collection of artifacts and other objects of scientific, artistic, cultural, or historical importance and makes them available for public viewing through exhibits that may be permanent or temporary. It can also be used to refer to a particular exhibit or collection within such a building or institution.
I like to go to the museum.
This sentence is expressing a personal preference about going to the museum. The 'ins' in the sentence is a contraction of 'in das', indicating a direction towards an indoor location, in this case, the museum.
The museum opens at nine o'clock.
This sentence is providing information on the operating hours of the museum. The word 'öffnet' is derived from 'öffnen', meaning 'to open', indicating the beginning of the operating hours.
Have you visited the museum?
In this question, the asker inquires if the person addressed has been to the museum. The phrase 'Hast du' is an informal way of saying 'Have you', and 'besucht' is the Past Participle of the verb 'besuchen', meaning 'to visit'.