Life in heaven or earthly paradise?

I have started to study the bible but wondered if any one could help explain why most religions teach that when we die we go to heaven. God made the earth for humans to live on, he made Adam and Eve first and he gave them paradise till they sinned but he also says in Psalms 104:5 He has founded the earth upon its established places; It will not be made to totter to time indefinite, or forever. and in other verses about the righteous possesing the earth. If we go to heaven when we die what will happen to the earth and why would God say the earth is forver if all those having faith and believe in God are going to heaven? I hope you understand what i am trying to say and please no rude comments!