Child to Parent, Parent to Child Data Passing in Lwc

ParentComponent.cmp:

<template>

    <div class="slds-m-around_small"  onsimple={handleSimpleEvent}>

        <p>I am inside of Parent Component</p>

        <c-child-comp

         message="pass message from parent compoent"

         pageno="37"

        ></c-child-comp>

    </div>

    <div class="slds-m-around_large">

        <lightning-button label="Change Date" variant="brand" onclick={handleClick}>

        </lightning-button>

    </div>

</template>

ParentComponent.js: 

import { LightningElement,api } from 'lwc';

export default class ParentComp extends LightningElement {

    @api messages="";

    @api pageno="";

    @api name="Md Sumon";

    handleSimpleEvent(event){

        this.messages = event.target.message;

        this.pageno = event.target.pageno;

        console.log("Message : "+this.messages);

        console.log("page no : "+this.pageno);

    }

    handleClick(){

        this.template.querySelector('c-child-comp').childMethod("After Api Function",120);

    }

}

------------------------------------------ Child Component--------------------------------------------------------

childComponent.cmp:

<template>

    <div class="slds-m-around_large">

        <p>I am Inside of child Component</p>

        <p>Message is : {message}</p>

        <p>PageNo is : {pageno}</p>

        <p>Date is : {date}</p>

        <lightning-button variant="brand" label="Create Event" onclick={handleEvent}>

        </lightning-button>

    </div>

</template>

childComponent.js:

import { LightningElement,api, track } from 'lwc';

export default class ChildComp extends LightningElement {

    @api message;

    @api pageno;

    @track date = new Date();

    

    @api

    childMethod(fromParent,pageNo){

        this.date = new Date();

        this.message = fromParent;

        this.pageno=pageNo;

    }

    handleEvent(){

        var newEvent = new CustomEvent('simple',

        {

            bubbles: true,

            composed: false

        }

        );

        this.dispatchEvent(newEvent);

    }

}