CustomLookupSelectionEvt.evt

<aura:event type="COMPONENT" description="On record selection">
    <aura:attribute name="childObjectName" type="String"/>
    <aura:attribute name="fieldName" type="String"/>
    <aura:attribute name="selectedRecordId" type="String"/>		    
</aura:event>

CustomLookupStd.cmp

<aura:component>
    <aura:attribute name="childObjectName" type="String" required="true"/> 
    <aura:attribute name="fieldName" type="String" required="true"/> 
    <aura:attribute name="selectedRecordId" type="String"/> 
    
    <aura:registerEvent name="onSelectEvt" type="c:CustomLookupSelectionEvt"/>
    
     <lightning:recordEditForm
            onload="{!c.setSelectedRecordId}"                   
            objectApiName="{!v.childObjectName}">
           <lightning:inputField aura:id="lookupField" variant="label-stacked" fieldName="{!v.fieldName}" onchange="{!c.fireOnSelectEvt}"/>
			
    </lightning:recordEditForm>
</aura:component>

CustomLookupStdController.js

({
    setSelectedRecordId: function(component, event, helper) {
        var selectedRecordId = component.get("v.selectedRecordId");
    	component.find("lookupField").set("v.value", selectedRecordId);	    
    },
    
    fireOnSelectEvt : function(component, event, helper) {
	var cmpEvent = component.getEvent("onSelectEvt");
        cmpEvent.setParams({
            "childObjectName": component.get("v.childObjectName"),
            "fieldName": component.get("v.fieldName"),
            "selectedRecordId": component.find("lookupField").get("v.value")
        });
        cmpEvent.fire();
    }
})

ParentComponent.cmp

<!--aura Handler-->
<aura:handler name="onSelectEvt" event="c:CustomLookupSelectionEvt" action="{!c.getLookUpValues}"/>
    
<c:CustomLookupStd
  selectedRecordId="{!v.projectId}"
  childObjectName="Contact" 
  fieldName="Project_in_Contact__c"/>

ParentComponentController.js

{
  getLookUpValues : function(component, event, helper){
        let fieldName = event.getParam("fieldName");
        let projectId = event.getParam("selectedRecordId");
        
        component.set("v.projectId", projectId);
    },
} 

works well but how to fetch more than one field from same obj like picklist