Is it permissible to pray in a mosque on which is written "The General Authority for Shrines and Graves"? And what is the ruling on continuing to work if the employer stipulates not closing the shop at prayer times, after the agreement was to pray in the mosque?

If there is a grave in the mosque, prayer in it is not permissible. However, if there is no grave in it, there is no harm in praying in it, while striving to remove the phrase "General Authority for Shrines and Graves" written on the mosque, because taking graves as mosques is an innovation that contradicts the guidance of the Prophet, peace and blessings be upon him, and texts have been reported warning against this. It is not permissible to put the name of the Authority for Shrines on mosques, and this should be denounced. As for an employer preventing someone from praying in the mosque, congregational prayer is obligatory and should not be abandoned except for an excuse. If you are forced to pray at your workplace, there is no harm upon you, while searching for someone to pray in congregation with you until you find another job where you can maintain congregational prayer in the mosque.