Ok, I will leave this here in case someone needs it.I didn't have problems entering the bootloader. The function is similar to what @gbm posted but with I additionally mapped the bootloader memory and set the CONTROL register to use the MSP. With tho...

Hello everyone hereThanks @m4l490n for your suggestion. It works fine here, but I have exactly the same problem as @AWack . After entering the bootloader and flashing the new application, the bootloader CAN NOT jump again to the new application code....