Modifying the VRAM size is not something any bios editor out there can do right now. It essentially involves recreating a good bit of the bios RAM tables with a hex editor.
I did it once for PhilsComputerLab and for someone else as fun. But never again.
Really I hope you got a refund and just get a proper gpu.
There’s so much wrong with these knock-off scam cards I don’t even know where to begin.