When Opportunity is created for Contact, get Contact details for Opportunity

 When Opportunity is created for Contact, get Contact details for Opportunity.

Use this as reference, write your own code -

trigger OpportunityTrigger on Opportunity (before insert) {
    Set<id> conIds = new Set<id>();
    for(Opportunity opt : Trigger.new){
        conIds.add(opt.Contact__c);
    }
    Map<Id,Contact> conMap = new Map<Id,Contact>();
    List<Contact> contacts = [SELECT id,Phone,Email FROM Contact WHERE Id IN : conIds];
    for(Contact con : contacts){
        conMap.put(con.Id, con);

    }
    for(Opportunity opt:trigger.new){    
        if(opt.Contact__c != null)
        {
            opt.Phone__c =conMap.get(opt.Contact__c).phone;
            opt.Email__c =conMap.get(opt.Contact__c).Email;
        }
    }
}