you have three varchar params, @Nev, @Cim and @Datum.
it seems you try to insert one of them to an integer column.
check Vasarlas and Vevo tables or better trap begin end blocks to determine which insert statement causes the error ...
by the way;
EXEC UjVasarlas 2, 2, 'Your Name', 'Your City', 2, '2013-01-22'
can not return error for "Cluj-Napoca" string which is not included in params you sent.
if "Cluj-Napoca" is in the 'Your city' space, it means your problem is @Cim param.
And u use it ın only one place, in else blog ;
INSERT INTO Vevo VALUES (@maxId+1, @Nev, @Cim, 1)
check the Table Vevo, probably 3th column of that table (which u try to insert @Cim param) is INT not VARCHAR