Well then, first things first.
You can see the image is inserted in webflow as an image (Note the image logo):
An image can only hold an uploaded image itself. Nothing else can be nested inside the image.
2 ways to perform what you want.
First is: Keep the image and set a relative or absolute position to the buttons. It´s a little cumbersome and you really need to know what you are doing else you are going to have some unwanted behavior.
Second is the best one if you ask me:
- Instead of using the image, place a normal DIV, and set the image as background of that DIV
- Delete the image
- Drag the buttons in the newly created DIV
- Use Flexbox for superior easy centering
- Enjoy your buttons on top of image
I think this is what you wanted?