Hello Abrar Ahmed,
You can set a class with the value width 100%; on the given widget, then the input box should stretch to the entire width.
.inputbox-widget {
width: 100%;}
You can test this directly on the page with the "inspect" tool on the element and add the value in the style element.
Hi, Abrar Ahmed
Please Add one more Layout below of current Layout set auto fill and add the text box want you want the input box should stretch to the entire width.
hope you help this
good luck!