java.sql.SQLException: The server time zone value - connecting using port and name

I'm filling in some text fields in my app and want to send them to the database "appforhh". But I get the error:

java.sql.SQLException: The server time zone value 'RTZ 2 (����)' is unrecognized or represents more than one time zone. You must configure either the server or JDBC driver (via the 'serverTimezone' configuration property) to use a more specifc time zone value if you want to utilize time zone support.

I tried SET GLOBAL time_zone = '+3:00'; in mySQL, but nothing changed.

public class DataBaseHandler extends Configs {
Connection dbConnetion;

public Connection getDbConnetion() throws ClassNotFoundException, SQLException {
    String connectionString = "jdbc:mysql://" //Connection String
            + dbHost + ":"
            + dbPort + "/"
            + dbName;
    Class.forName("com.mysql.cj.jdbc.Driver");
    dbConnetion = DriverManager.getConnection(connectionString, dbUser, dbPass);
    return dbConnetion;
}