import { timeline } from 'wix-animations';
import wixWindow from 'wix-window';

$w.onReady(function () {
    txtScroll()

 function txtScroll() {
        wixWindow.getBoundingRect()
            .then((windowSizeInfo) => {
 let scrollY = windowSizeInfo.scroll.y;
                timeline().add($w('#mytxt'), { x: scrollY, duration: 100 }).play();
            });
        setTimeout(txtScroll, 10);
    }
});

Also, in order to maintain good performance on your website, it's recommended to disable animations when scrolling past element's viewport. So I would suggest adding export function section4_viewportEnter(event) as trigger.