Merging a node from one XML to another with same attribute in XML using C#

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C#

SQL

First XML

<Result>
  <subject_premium />
  <flatrate />
  <Result_system skip_name="skipname 1- order" skip="skip_1" type="freeform">
    <order>
      <Address include="1">CO</Address>
    </order>
  </Result_system>
  <Result_system skip_name="Formula 1 - Renewal Business Incentive" skip="skip_2" type="freeform">
    <order />
  </Result_system>
  <Result_system skip_name="Formula 2 - New Business Incentive" skip="skip_3" type="freeform">
    <order />
  </Result_system>
  <Result_system skip_name="skipname 2" skip="skip_4" type="Custom">
    <FinalResult>
      <Name />
      <sequence>1</sequence>
      <Remape>12333</Remape>
      <Limit>66</Limit>
    </FinalResult>
    <order />
  </Result_system>
  <Result_system skip_name="skipname - 3" skip="skip_5" type="Custom">
    <FinalResult>
      <Name />
      <sequence>1</sequence>
      <NBTS>888</NBTS>
      <LMS>423</LMS>
    </FinalResult>
    <order />
  </Result_system>
  <Result_system skip_name="skipname - 4" skip="skip_6" type="Custom">
    <FinalResult>
      <Name />
      <sequence>1</sequence>
      <Count>74</Count>
      <Sum>16</Sum>
      <Address>GA</Address>
    </FinalResult>
    <order />
  </Result_system>
</Result>

Second XML

'<Result>
  <subject_premium />
  <flatrate />
  <Result_system skip_name="skipname 1- order" skip="skip_1" type="freeform">
    <order>
      <Address include="1">CO</Address>
    </order>
  </Result_system>
  <Result_system skip_name="Formula 1 - Renewal Business Incentive" skip="skip_2" type="freeform">
    <order />
  </Result_system>
  <Result_system skip_name="Formula 2 - New Business Incentive" skip="skip_3" type="freeform">
    <order />
  </Result_system>
  <Result_system skip_name="skipname 2" skip="skip_4" type="Custom">
    <FinalResult>
      <Name>Tom</Name>
      <sequence>1</sequence>
      <Remape>162</Remape>
      <Limit>1254</Limit>
    </FinalResult>
    <order />
  </Result_system>
  <Result_system skip_name="skipname - 3" skip="skip_5" type="Custom">
    <FinalResult>
      <Name>Sammy</Name>
      <sequence>1</sequence>
      <NBTS>231</NBTS>
      <LMS>145</LMS>
    </FinalResult>
    <order />
  </Result_system>
  <Result_system skip_name="skipname - 4" skip="skip_6" type="Custom">
    <FinalResult>
      <Name>John</Name>
      <sequence>1</sequence>
      <Count>21</Count>
      <Sum>16</Sum>
      <Address>GA</Address>
    </FinalResult>
    <order />
  </Result_system>
</Result>'

I want to merge <finalresult> node from second xml to first xml with matching attribute of skip

and want to merge only in node element attribute skip_4, skip_5 and skip_6

skip="skip_4"

should be match with

skip="skip_4"

and

skip="skip_5"

should be match with

skip="skip_5"

and

skip="skip_6"

should be match with

skip="skip_6"

The result should be like

<Result>
  <subject_premium />
  <flatrate />
  <Result_system skip_name="skipname 1- order" skip="skip_1" type="freeform">
    <order>
      <Address include="1">CO</Address>
    </order>
  </Result_system>
  <Result_system skip_name="Formula 1 - Renewal Business Incentive" skip="skip_2" type="freeform">
    <order />
  </Result_system>
  <Result_system skip_name="Formula 2 - New Business Incentive" skip="skip_3" type="freeform">
    <order />
  </Result_system>
  <Result_system skip_name="skipname 2" skip="skip_4" type="Custom">
    <FinalResult>
      <Name>
      <sequence>1</sequence>
      <Remape>12333</Remape>
      <Limit>66</Limit>
    </FinalResult>
	<FinalResult>
      <Name>Tom</Name>
      <sequence>1</sequence>
      <Remape>162</Remape>
      <Limit>1254</Limit>
    </FinalResult>
    <order />
  </Result_system>
  <Result_system skip_name="skipname - 3" skip="skip_5" type="Custom">
    <FinalResult>
      <Name />
      <sequence>1</sequence>
      <NBTS>888</NBTS>
      <LMS>423</LMS>
    </FinalResult>
	 <FinalResult>
      <Name>Sammy</Name>
      <sequence>1</sequence>
      <NBTS>231</NBTS>
      <LMS>145</LMS>
    </FinalResult>
    <order />
  </Result_system>
  <Result_system skip_name="skipname - 4" skip="skip_6" type="Custom">
    <FinalResult>
      <Name />
      <sequence>1</sequence>
      <Count>74</Count>
      <Sum>16</Sum>
      <Address>GA</Address>
    </FinalResult>
	 <FinalResult>
      <Name>John</Name>
      <sequence>1</sequence>
      <Count>21</Count>
      <Sum>16</Sum>
      <Address>GA</Address>
    </FinalResult>
    <order />
  </Result_system>
</Result>'

What I have tried:

I have tried with SQL but it is only updating first node.
In C# I am able to navigate under XMLElement but not getting how to add an element value within an element.

Please guide a bit