The code posted in your question is not well-formed xml which is why DOMParser wasn't working. But if your actual code is something like the below, the following should work:

let xmldoc = `<?xml version="1.0" encoding="UTF-8"?>
<root>
   <XYZNetWebService xmlns="http://abcdefs"/>
<XYZNetResponse Guid="asfdsafdsa23c6" LastAccess="2022-02-24" Report="Projects" Parameter="" status="200"/>
<Project>
    <ProjectNr>505</ProjectNr>
    <Description>Testproject</Description>
</Project>
<Project>
    <ProjectNr>123</ProjectNr>
    <Description>Project2</Description>
</Project>
</root>`;

const data = new DOMParser().parseFromString(xmldoc, 'text/xml');
let x = data.evaluate("//Project", data, null, XPathResult.ORDERED_NODE_SNAPSHOT_TYPE, null);
for (let i = 0; i < x.snapshotLength; i++) {
  let tags = data.evaluate('.//*', x.snapshotItem(i), null, XPathResult.ORDERED_NODE_SNAPSHOT_TYPE, null);
  for (let i = 0; i < tags.snapshotLength; i++) {
    console.log(tags.snapshotItem(i).textContent);
  }
}

Output would be

"505"
"Testproject"
"123"
"Project2"

The XML seems to use a default namespace (xmlns="http://abcdefs"). This means that the node Project has to be read as {http://abcdefs}Project.

Here is set of namespace aware methods (with the suffix NS) that take the expected namespace as an argument.

Xpath expression need a resolver - and they don't have a default namespace. The prefixes you're using in the Xpath expression are separate from the XML source. Which makes sense because the XML is an external source and could change.

I am using nws in the following example. So //nws:Project can be read as //{http://abcdefs}Project

const output = document.querySelector('#demo');

const resolver = function(prefix) {
    const namespaces = {
        nws: 'http://abcdefs'
    }
    return namespaces[prefix || ''] || null;
}

const data = new DOMParser().parseFromString(getXMLString(), 'text/xml');
const projects = data.evaluate(
    "//nws:Project", data, resolver, XPathResult.ANY_TYPE, null
);
let project;
while (project = projects.iterateNext()) {
    
    const projectNr = data.evaluate(
        'string(nws:ProjectNr)', project, resolver, XPathResult.STRING_RESULT, null
    ).stringValue;
    const description = data.evaluate(
        'string(nws:Description)', project, resolver, XPathResult.STRING_RESULT, null
    ).stringValue;
    
    output 
        .appendChild(document.createElement('li'))
        .textContent = `${projectNr}: ${description}`;
}

function getXMLString() {
    return `<?xml version="1.0" encoding="UTF-8"?>
    <XYZNetWebService xmlns="http://abcdefs">
      <XYZNetResponse Guid="asfdsafdsa23c6" LastAccess="2022-02-24" Report="Projects" Parameter="" status="200">
        <Project>
          <ProjectNr>505</ProjectNr>
          <Description>Testproject</Description>
        </Project>
        <Project>
          <ProjectNr>123</ProjectNr>
          <Description>Project2</Description>
        </Project>
      </XYZNetResponse>
    </XYZNetWebService>`
};

<ul id="demo">

</ul>

you can transform with camaro like this

const { transform } = require('camaro')

async function main() {
    const xml = `
<XYZNetWebService xmlns="http://abcdefs">
<XYZNetResponse Guid="asfdsafdsa23c6" 
LastAccess="2022-02-24" Report="Projects" Parameter="" status="200">
<Project>
    <ProjectNr>505</ProjectNr>
    <Description>Testproject</Description>
</Project>
<Project>
    <ProjectNr>123</ProjectNr>
    <Description>Project2</Description>
</Project>
</XYZNetResponse>
</XYZNetWebService>
`

    const template = {
        projectNr: ['//Project', 'ProjectNr'],
        projectDesc: ['//Project', 'Description']
    }
    const output = await transform(xml, template)
    console.log(output);
}

main()

output

{
  projectNr: [ '505', '123' ],
  projectDesc: [ 'Testproject', 'Project2' ]
}