the reverse ( backup ) lights are not working How can I solve the problem

Thank you for your response It is manual transmission

As zippie1 suggested, test the fuses first .. In the owners manual index (back pages of book) look up fuses then go to the appropriate page for fuse location information .. Check the fuse .. It is possible the back-up light switch on the transmission has failed... That is more than likely not a DIY fix... Also possible, but not quite as likely, is both bulbs or wiring to the bulbs is the culprit... (Blown fuse is first suspect.)