Sticky scroll applied to specific section ID

Site URL: https://www.poppyandseedstudio.com.au/

I want the 'Discovery, Development & Delivery' cards to stack on top of each other as you scroll for mobile view only.

This is the code I've got however its not working - 

@media only screen and (max-width: 768px) {
    section[data-section-id="67050ce4e28f7b16df3c1b78"] {
        position: relative;}

    section[data-section-id="67050ce4e28f7b16df3c1b78"] #block-yui_3_17_2_1_1728383974721_11285,
    section[data-section-id="67050ce4e28f7b16df3c1b78"] #block-730e5033a4235ddda5e2,
    section[data-section-id="67050ce4e28f7b16df3c1b78"] #yui_3_17_2_1_1728428847905_511 {
        position: -webkit-sticky;
        position: sticky;
        top: 0; /* Stick to the top of the viewport */
        z-index: 10;}

    section[data-section-id="67050ce4e28f7b16df3c1b78"] #block-yui_3_17_2_1_1728383974721_11285 {
        z-index: 30;
    }

    section[data-section-id="67050ce4e28f7b16df3c1b78"] #block-730e5033a4235ddda5e2 {
        z-index: 20;
    }

    section[data-section-id="67050ce4e28f7b16df3c1b78"] #yui_3_17_2_1_1728428847905_511 {
        z-index: 10;
    }
}

You try this CSS code

@media screen and (max-width:767px) {
.fe-block-yui_3_17_2_1_1728383974721_11285 {
    position: sticky;
    top: 0;
}
.fe-block-730e5033a4235ddda5e2, .fe-block-88fef4c6aa04912cb985 {
    position: sticky;
    top: 0;
}
}