It seems like you are referring to the character John Nash, portrayed by Russell Crowe in the movie "A Beautiful Mind." John Nash was a real-life mathematician who struggled with schizophrenia.
In the movie, his experiences with schizophrenia are depicted, and he indeed saw and interacted with people who were not real, such as Charles Hermann, Marcee, and William Parcher. These characters were part of his delusions and hallucinations, which are common symptoms of schizophrenia. For him, these imaginary people appeared as if they were real, and he had difficulty distinguishing between reality and his delusions.
In reality, John Nash did suffer from paranoid schizophrenia and experienced similar hallucinations and delusions. However, it's important to remember that movies often take creative liberties and dramatize events for storytelling purposes. While "A Beautiful Mind" provides a glimpse into John Nash's life and his struggles with mental illness, it may not fully capture the complexities of his actual experiences.