Potential solution

In[]:=
values=Sort[{{"5",1,2,3},{"1",4,5,6},{"5",7,6,7},{"2",8,9,10},{"2",8,9,10}}];​​keys={"group","num 1","num 2","num 3"};​​table=PivotFromColumns[Tabular[values,keys],{"num 1","num 2","num 3"}->{"position","value"}];​​pivotTable=PivotTable[table,Total[#["value"]]&,"group","position",IncludeGroupAggregates->True];​​Tabular[pivotTable,Background-><|"RowRules"->{-1->
},"ColumnRules"->{-1->
}|>]
Out[]=
Tabular
Row count: 4
Column count: 5
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