How to create Custom Lookup field in lightning-input which fetch the user name?

I want to create custom lookup field without using lightning-edit-record-form. Notify to when completed = lookup(users), its not fetching the users name. Here is what I coded:

<lightning-input

              class="requiredfield"
              type="search"
              name="notifyToWhenCompleted"
              variant="label-hidden"
              placeholder="Search Users" 
              value={userName}
              onchange={myLookupHandle} onkeydown={searchHandleClick} onclick={searchHandleClick}
              style="padding-bottom:20px; width:275px; font-weight:normal; color:#424345;">
             </lightning-input>

JS
myLookupHandle(event){
   console.log(event.detail);
   this.milestoneId = event.detail;
   this.userName = event.target.value;
}
 searchHandleClick(event){
    this.isShowResult = true;
    this.messageResult = false;
 }
  
  searchHandleKeyChange(event){
   this.messageResult=false;
   this.userName = event.target.value;
 }