How to expand the time width of small part of a signal with the total time width of the signal be same?

Here I have the signal as shown above, but I need to expand the time width of the signal in the portions that is marked in red colour i.e, the width of the given portion marked in red colour is 10 (15 to 25, as shown in fig.), but I need to increase the width by 20. However, the total width of the signal should not be changed i.e, 40.