change quantity position selector [Woocommerce]

1) this is my product page layout:
https://node5040.myfcloud.com/~examenesadomicil/producto/pcr-a-domicilio/
I want to add a cart summary similar to this one (also fixed when scrolldown)
https://examenesadomicilio.com/producto/pcr-a-domicilio/
Please I need it to be done without replacing original woocommerce files. It has to be updated on child-theme.

1)
1) this is my product page layout:
https://node5040.myfcloud.com/~examenesadomicil/producto/pcr-a-domicilio/
I need to move the quantity selector from the bottom to the top of the product, same as the following referencial site and change design, similar to the quantity selector of https://examenesadomicilio.com/producto/pcr-a-domicilio/

Both sites are mine, so you can access code of referencial site if needed.