Ralf, eat your Wheaties before you try to stretch those springs in place. I replaced a brake pedal on my 630.
The spring was easier to get off than back on. I clamped the largest Vice Grip pliers I had on the straight part of the spring behind the hook and pulled it in place. Use the outer most end of the pliers to avoid introducing stress notches in the spring which could promote a brittle failure of the spring over time.