C++, cannot assign/copy objects

So i have a class which is defined by:

class Interval{
    public:
       double upperLimit;
       double lowerLimit;
       double function[5];
       Interval *interval;
     };

At one point i declare two objects of the type Interval:

Interval interval;
Interval cInterval;

and i get two types of errors:

1) when i make an assignment like this:

cInterval.interval = &interval

I get an error : a value of type "Interval *" cannot be assigned to an entity of type "Interval *"

2) Also when i try to copy the objects:

interval = &cInterval

or

interval = cInterval

i get an error no operator "=" matches these operands -- operand types are: Interval = Interval

In first case both are pointer so i'm not sure why it's not working, in second case i've also tried to overload '=' operator but it still gave me this error (shouldn't be default '=' operator be implemented anyway ?).