As a start have a look at Photoshop's Image Processor, you can also run an Action with it.
Thank you and sorry for my late response.
Now I know how to record a action but how do I make a action when all the sizes are different?
If I make an action that adapts the height of the picture so that it is 1:1, what would happen when the width is larger and I need to adapt to the width.
And would the Photoshop know that I want the pictures to be in the center when I do the action?
Just wanted to inform that this problem has been solved.
Somebody gave me this script to solve