Rules: after saving new content and after updating existing content both triggered on node create I define two rules that should send an email once new node has been created. And second rule once user updated his content.

The problem I am having here is that both rules trigger in one time when your create a new node.

I found the same issue has been asked in anther question but not very clear and i am not able to understand enter link description here

But I am not able to understand.

Thanks for the help.
This is very easy to accomplish, you have a few attributes of the node to compare and check in order to decide which trigger to be true/false. 

Method 1: 
Put the following PHP code into your both conditions (create &amp; update) by selecting execute PHP code

CREATE

if($node-&gt;created == $node-&gt;changed) { 
   return true; 
} else { 
   return false; 
}


UPDATE 

if($node-&gt;created != $node-&gt;changed) {
    return true; 
} else { 
   return false; 
} 


Method 2:

UPDATE: 

if($node-&gt;is_new) {
     return false; 
} else {
     return true; 
}


OR

if(!empty($node-&gt;nid)) {
    return true; 
} else {
    return false; 
}


I have not checked the Method 2 but, method 1 is easier and should definitely work out for you. 

Don't forget to Accept this answer solve your problem. 

Cheers.

Raf.