Add spaces: Originallyprovedfora2-dimensionalsphere,Brouwerlatergeneralisedtheresulttospheresinndimensions.

Answer: Originally proved for a 2-dimensional sphere, Brouwer later generalised the result to spheres in n dimensions.

Add spaces: Theartistswillservearefreshment.

Answer: The artists will serve a refreshment.

Add spaces: Theoperator,whowasentrustedwithcodedmessages,wasisolatedinhisownlittleroom.Wecanseethesergeantbehindatelex-machine.

Answer:
The operator, who was entrusted with coded messages, was isolated in his own little room. We can see the sergeant behind a telex-machine.