First Supermassive Black Holes and Structure Formation -- Observations of Supermassive Black Holes at Higher Redshift -- Observations of Super Massive Black Holes in the Local Universe -- The Case of Sagittarius A* -- Interaction of Supermassive Black Holes with Their Environment -- Physics of Accretion Discs Around Supermassive Black Holes -- Black Hole–Black Hole Mergers and Gravitational W…