I use STM32H742xI/G and I used the internal RAM to buffer for the display and buffer for keep data and the RAM is devided and i cant to extend the buffer of the keep data cause its passed from the memory part how i solve it?

Use DTCM RAM (128k at 0x20000000) for program variables, AXI SRAM (384k at 0x24000000) for the display framebuffer, SRAM1/2/4 for DMA buffers if applicable. See the memory map in chapter 4 of the datasheet.

See your linker documentation on how to assign a different memory area for variables.

Use a pointer instead of an array for the framebuffer, for example

uint16_t *framebuffer = (uint16_t *)0x24000000;