Low brightness after 5 -6 hours

my 5 day old projector loses more and more brightness the longer I look. After 5-6 hours I am not able to watching because the picture is horrible. I need help.

Hello! Are you watching in a closed room without any natural lighting? Or are you in a room which has windows? As it may affect the brightness of the room as the hours pass. Also, are projecting on the wall or a projector screen? Thank you.