How to insert data into tables which reference each other?(MySQL)
Not sure I understood the task, but here is some food for thought for an alternative schema:

CREATE TABLE Departament(
    DepartamentID varchar(25) not null,
    Floor varchar(25) not null,
        CONSTRAINT pk_dept PRIMARY KEY (DepartamentID, Floor),
) ENGINE=InnoDB;


CREATE TABLE Employee(
    ID varchar(25) not null,
    DepartamentID varchar(25),
    Floor varchar(25),
        CONSTRAINT pk_ID PRIMARY KEY (ID),
        CONSTRAINT fk_dept FOREIGN KEY (DepartamentID, Floor) 
            REFERENCES Departament (DepartamentID, Floor)
) ENGINE=InnoDB;

CREATE TABLE Attendant (
    ID varchar(25) not null,
    DepartamentID varchar(25) not null,
    Floor varchar(25) not null,

    CONSTRAINT pk_attendent PRIMARY KEY (ID),
    CONSTRAINT ak_attendent UNIQUE (DepartamentID, Floor),
    CONSTRAINT fk_... REFERENCES Employee ...,
    CONSTRAINT fk_... REFERENCES Department ...,
) ENGINE=InnoDB;