Need help with a calculation

Anonymous - Like I said - you could use the approach from the thread that I linked to.

I have created a test with the data you provided:

So I start with a source table looking like this:

And from this table I create the table needed to make the wanted calculations:

Here is the Power Query code for this transformation:

let
    Source = SourceTable,
    ChangedType = Table.TransformColumnTypes(Source,{{"AptId", type text}, {"einzug", type date}, {"auszug", type date}, {"Moveout", type text}, {"MoveIn", type text}}),

    InDate = Table.SelectColumns(ChangedType, {"AptId", "einzug"}),
    InDate_InOut = Table.AddColumn(InDate, "In/Out", each "In"),
    InDate_Count = Table.AddColumn(InDate_InOut, "Count", each 1),
    InDate_RenameColumn = Table.RenameColumns(InDate_Count, {{"einzug", "Date"}}),

    OutDate = Table.SelectColumns(Table.SelectRows(ChangedType, each [auszug] <> null), {"AptId", "auszug"}),
    OutDate_InOut = Table.AddColumn(OutDate, "In/Out", each "Out"),
    OutDate_Count = Table.AddColumn(OutDate_InOut, "Count", each -1),
    OutDate_RenameColumn = Table.RenameColumns(OutDate_Count, {{"auszug", "Date"}}),

    AppendInOut = Table.Combine({InDate_RenameColumn, OutDate_RenameColumn}),
    ChangedType2 = Table.TransformColumnTypes(AppendInOut,{{"Count", Int64.Type}})
in
    ChangedType2

I also added the date table like in the example that I posted - created the needed relationship between the tables and made 4 measures:

MoveIn = 
CALCULATE(
    SUM( Tabel1[Count] );
    Tabel1[In/Out] = "In"
)

MoveOut = 
CALCULATE(
    -SUM( Tabel1[Count] );
    Tabel1[In/Out] = "Out"
)

Diff In/Out = [MoveIn] - [MoveOut]

Appartments with tenants = 
VAR MaxDate = CALCULATE( MAX( Tabel1[Date] ); ALL( 'Date' ) )
RETURN
IF(
    MIN( 'Date'[Date] ) <= MaxDate;
    CALCULATE(
        SUM( Tabel1[Count] );
        DATESBETWEEN( 'Date'[Date]; BLANK(); MAX( 'Date'[Date] ) )
    )
)

Here is my result - the top table show what you are asking for - the barchart show the measure "Appartments with tenants" by year (this could be taken a step further if you had the info about when an appartment was available from (and to) to calculate the number of total appartment available at a given date and then you could calculate the % of how many of the appartments that had tenants at any given time.