Complex sentence: Like Antoine, he took an apartment across the street from hers so that he could monitor her activities, but she was ultimately not interested in him or any of his friends (she had also attracted attention from Jean Gruault and Jean-Luc Godard).
Split into simpler sentences: Like Antoine, he took an apartment across the street from hers so that he could monitor her activities. However, she was ultimately not interested in him nor in any of his friends (she had also attracted attention from Jean Gruault and Jean-Luc Godard).