The thoughts of Jean-Paul Sartre do not relate to Christianity.
Christianity means we believe in Jesus; that we are saved unto eternal life by the precious blood of Jesus. And Jean-Paul Sartre's thoughts show a diversity from this. When he was asked how he would like to be remembered, he said:
"I would like people to remember the milieu or historical situation in which I lived,... how I lived in it, in terms of all the aspirations which I tried to gather up within myself. "
So his thoughts were on himself and not on our Lord Jesus Christ.