Problems with variable definition in Powerapps - variables

Question

the issue is that the variable definition is incorrect in some way.
varTischNr was set with Set() and now with "=". Both unfortunately achieved the effect when replicating the code that varTableNr either always remains 1 or something else happens. Not sure. Before, instead of varTischNr, there was the respective number, in this case a 1.
The code should show the name of the logged in user when clicking on the image and should create an entry in the table 'tbl_S4.E2.03-05'.
Translaions:
Tisch = Table
Buchungen = Bookings
Anzahl Eintraege = Number of entries
Buchungsdatum = Booking date
Part of the Code:
varTischNr="1";;
If(Concat(Filter(colBuchungenTag;Tisch2=varTischNr);Title)=(
Left(User().FullName;1) &
Mid(
User().FullName;
Find(" "; User().FullName) + 1;
2)
);
Set(varAnzahlEintraege;Count(Filter('tbl_S4.E2.03-05';Tisch2=varTischNr;Buchungsdatum=varTag.Datum).ID)
);;
If(varAnzahlEintraege>0;
Remove('tbl_S4.E2.03-05';
Filter('tbl_S4.E2.03-05';Tisch2=varTischNr;Buchungsdatum=varTag.Datum));;
;
ClearCollect(colBuchungenTag;Filter('tbl_S4.E2.03-05';Buchungsdatum=varTag.Datum));;Select(btn_Refresh);;
);;
Notify("Buchung erfolgreich gelöscht";NotificationType.Error);;
ClearCollect(colBuchungenTag;Filter('tbl_S4.E2.03-05';Buchungsdatum=varTag.Datum));;
Select(btn_Refresh)
;Notify("Der Tisch kann nur vom Besitzer freigegeben werden";NotificationType.Information))
The goal should be that varTischNr works and the entries for 'tbl_S4.E2.03-05' are replaced by variables.