Comparison problems with Grafana variables

[j-prall]

Hi,
at first, I´m working with the Grafana version 7.4.5, with the MongoDb version 4.4 and I´m running it on a lokal host.

I want to filter my Dashboard Variables with multiple variables.
My first Panel shows the variable value and the second panel shows the data i want to filter.

The Panels show data if i choose a specific value of the variables but don´t show something when i choose multiple values.

one value selected

multiple values selected

the query for the comparison is here:
db.berichte2.aggregate ( [{"$match": {
"etestresult.test.results.testcase.@Result": {"$eq": "failed"}
}}, {"$unwind": {
"path": "$etestresult.test.measurands.measurand"
}}, {"$match": {
"etestresult.test.measurands.measurand.@module": {"$eq": "Projektbeschreibung"}
}}, {"$group": {
"_id": {"id": "$etestresult.test.@EndTime"},
"Name": {"$push": "$etestresult.test.measurands.measurand.@name"},
"value": {"$push": "$etestresult.test.measurands.measurand.@value"}
}}, {"$project": {
"ts": {"$toDate": "$_id.id"},
"Maschinentyp": {"$arrayElemAt": ["$value", 0]},
"Maschinenbezeichnung": {"$arrayElemAt": ["$value", 1]},
"Maschinennummer": {"$arrayElemAt": ["$value", 2]},
"SVN-Stand": {"$arrayElemAt": ["$value", 3]},
"_id": 0
}},
{"$match": {"Maschinentyp": {"$eq": "$maschine"}}},
{"$match": {"Maschinenbezeichnung": {"$eq": "$bezeichnung"}}}])

as you can see I just match the variables "$maschine" and "$bezeichnung" with strings of my data.

I don´t find a solution to my Problem but really need one.