Change integrated Form width

Hi Everyone! The owner of the following website signed up for a donation form that can be integrated into the website. Now I got the code and put it on the site: https://stadtmuur.ch/spenden/ Now, however, I do not want it to be full width, but more like the example the donation-company send me too: https://tamaro.raisenow.com/verei-79e1/latest/index.html How can I change the width of this block? Thanks and kind regards Kevin