How to query for only the joint nodes in between

Users
2

Not sure if I understood perfectly. But for

“I want to find the “projects” that they mutually work on.”

You can do something like:

Take into account that I had to improvise by simplifying the sample.

{
  company1(func: type(Company)) 
  @filter(eq(name, "Equinor ASA") ) {
    uid
    name
    PC1 as ~project.company
    count(~project.company)
  }
  company2(func: type(Company)) 
  @filter(eq(name, "Royal Dutch Shell") ) {
    uid
    PC2 as ~project.company
    count(~project.company)
  }
  
  worked(func: uid(PC1)) @filter(uid(PC2)) {
    name
    ~project.company {
      name
    }
     count(uid)
  }
    
}

Result

{
  "data": {
    "company1": [
      {
        "uid": "0xea6f",
        "name": "Equinor ASA",
        "count(~project.company)": 6
      }
    ],
    "company2": [
      {
        "uid": "0xea70",
        "name": "Royal Dutch Shell",
        "count(~project.company)": 6
      }
    ],
    "worked": [
      {
        "count": 4
      },
      {
        "name": "Worked with Shell 1"
      },
      {
        "name": "Worked with Shell 3"
      },
      {
        "name": "Worked with Shell 2"
      },
      {
        "name": "Worked with Shell 4"
      }
    ]
  }
}

Mutation

{
	"set": [{
			"uid": "_:EquinorASA",
			"name": "Equinor ASA",
			"dgraph.type": "Company"
		},
		{
			"uid": "_:Shell",
			"name": "Royal Dutch Shell",
			"dgraph.type": "Company"
		}, {
			"name": "the Timor Sea",
			"project.company": {
				"uid": "_:EquinorASA"
			}
		},
		{
			"name": "the Canyon Lime formation",
			"project.company": {
				"uid": "_:EquinorASA"
			}
		}, {
			"uid": "_:Shell1",
			"name": "Worked with Shell 1",
			"project.company": [{
				"uid": "_:EquinorASA"
			}, {
				"uid": "_:Shell"
			}]
		}, {
			"uid": "_:Shell2",
			"name": "Worked with Shell 2",
			"project.company": [{
				"uid": "_:EquinorASA"
			}, {
				"uid": "_:Shell"
			}]
		}, {
			"uid": "_:Shell3",
			"name": "Worked with Shell 3",
			"project.company": [{
				"uid": "_:EquinorASA"
			}, {
				"uid": "_:Shell"
			}]
		}, {
			"uid": "_:Shell4",
			"name": "Worked with Shell 4",
			"project.company": [{
				"uid": "_:EquinorASA"
			}, {
				"uid": "_:Shell"
			}]
		}, {
			"name": "Tobago",
			"project.company": {
				"uid": "_:Shell"
			}
		}, {
			"name": "the Hazira LNG and Port venture",
			"project.company": {
				"uid": "_:Shell"
			}
		}
	]
}