Hi Aisha Khan,

Please add the below Custom CSS code to Theme Settings > Custom CSS > Global Custom CSS for Mobile sections:

.wd-coupon-form input.input-text{
	max-width: 50%;
}

.cart-actions button.button{
	width: 50%;
}

.coupon.wd-coupon-form {
	flex-direction: row;
margin-bottom: 20px;
}

Regards,