I thought he was a forgiving god?
Well yes!, you thought right!..He is indeed a forgiving God as well as a just God, furthermore He is also all knowing, all powerful, all loving, just a supremely good God!
He is so good and forgiving that He gave His only begotten Son Jesus Christ our Lord Savior to pay for all the sins of mankind that whoever believes in Him will not persish but will have eternal life (John 3:6).
So He gives everyone this forgiveness but this choice to accept or reject this forgiveness has to be made while you are still living here on earth and not when you are facing Him at Judgment Day because it will too late to tell Him, "Ok Lord!, I accept your only begotten Son Jesus Christ as my Lord Savior"
So this free choice everyone has will determine their eternal destiny.
Some will spend eternity in paradise in God's Kingdom of Heaven with Him and others who are saved and will live happily ever after.
Most will spend eternity in the pits of hell where the lake of fire burns and the cries of weeping are heard with the gnashing of teeth. This is a place where satan and his demons will also reside.
Does this help you to understand that He is indeed a forgiving and just God?