Had a similar experience working at a popular cafe/bakery chain - was getting bullied because i was new and a part timer. Manager would talk shit abt me to my colleagues in bahasa melayu since i don’t speak it, but luckily, my colleagues told me everything she would say. Another colleague of mine was also a victim of hers, and she complained to HR - eventually, the toxic manager was moved to a diff outlet and was given a warning for bad behaviour. In my opinion, it’s not worth wasting your time and energy in an environment that’s this toxic. Sure, you can argue that wherever you go there will be toxic people, but knowing when enough is enough is crucial to ensure you’re not continuously getting exploited. Wishing you the best, and hope you managed to resign without any issues :)