magento2 – Add a new class to fieldset ko html

On mobile, on checkout page, i have five zones like in below picture. And i want, at the begining, only the first zone to be expanded,number 1 and number 2, 3, 4, 5 to be contracted(for example to appear only the number and the title). After you complete the fieldset on number 1 and press the button(each element has their own button) i want to second zone to expand and the first one to contract. For these i created two classes: show-element and hide-element and when i press the button i want the second element fieldset to have besides his class another class: show-element and the first element fieldset to add hide-element class. And so on with until 5. My question is how i can do this or something like this, unfortunelly every element have his own html: shipping, email, form, billing-address, list. Thank you! enter image description here