We drained our pool this summer to straighten up the liner. We had to pull the liner up one side and after partial refilling the walls collapsed just on that side. Can the walls be staightened? We are buying a new liner also.

It is possible to fix them if the walls are not to damaged

You can not reposition an old liner, they are to brittle and will not assume the new shape you want, but you already found that out. What brand pool do you have? The ones I have worked on can not do what you describe since the top seat around the pool would prevent collapse.