I´ve got another problem with my PowerApps project.

The following code should mark the loan and return dates, which are listed in a SharePoint list, in the calendar from my Power App. The goal is to use the calendar as an overview, to see which and how long we loan devices to our Coworkers (I'm in the IT-Team).

If(
    CountRows(Filter(Ausgaben2;
        DateValue(ThisItem.Value) >= DateValue(Ausleihdatum);
        DateValue(ThisItem.Value) <= DateValue(Rückgabedatum)
    )) > 0;
    RGBA(255; 0; 0; 0,8); // Rot für gebuchte Tage
    RGBA(255; 255; 255; 1) // Standardfarbe für freie Tage
)

The name of the SharePoint list is "Ausgaben2", the columns in the SharePoint list, which show from when to when Devices get loaned, are Date&Time fields. They´re called "Ausleihdatum" (Loandate) and "Rückgabedatum" (Returndate).

I get an error marked in this line of code:

DateValue(ThisItem.Ausleihdatum) >= DateValue(Ausleihdatum);
DateValue(ThisItem.Rückgabedatum) <= DateValue(Rückgabedatum)

"Ausleihdatum" is an error, although the columns in my SharePoint list have these exact names.

I´ve added 2 pictures which show the code and error, and the SharePoint list I'm working with.

I would be really happy if someone could help me :)