Your code is getting them all.
levels
is of type
"System.Linq.Enumerable+WhereEnumerableIterator`1[System.Xml.Linq.XElement]"
so it contains a "list" of the matching nodes.
You can filter it further on the read
var levels = from levl in xmlDoc.Descendants()
where (levl.Name.LocalName == "ExecutionType" && levl.Parent.Name == "Level")
select levl;
or you can determine what the parent node is when you are using the data (which I guess is what you need as you said "I want to get them separately")
E.g.
foreach (var l in levels)
{
Console.WriteLine(l.Parent.Name);
}