In book 7, Voldemort visits Grindelwald at Nurmengard in order to interrogate him about the location of the Elder Wand, and then kills him. So Grindelwald was definitely alive in book 1.
In book 7, Voldemort visits Grindelwald at Nurmengard in order to interrogate him about the location of the Elder Wand, and then kills him. So Grindelwald was definitely alive in book 1.