I need help to start a project for STM32f407vg

I'm starting with programming on these boards
I have no experience or arduino

this is the code:

#include "stm32f4xx.h"                  // Device header

int main(){
        GPIO_InitTypeDef a;
}

The program marks me error where it says: GPIO_InitTypeDef a;
error: use of undeclared indentifier 'GPIO_InitTypeDef'

When I compile this:

compiling cmsis_rv.c...
D:\keil\Demo14\RTE\CMSIS_RTOS_Validation\RV_Config.h(10): error: #5: cannot open source input file "ARMCM3.h": No such file or directory #include "ARMCM3.h"
C:\Keil_v5\ARM\PACK\ARM\CMSIS-RTOS_Validation\1.1.0\Source\cmsis_rv.c: 0 warnings, 1 error
".\Objects\Demo14.axf" - 4 Error(s), 1 Warning(s).
Target not created.
Build Time Elapsed: 00:00:10

I have done it as it is in the tutorials.
I've tried copying the Blinky sample routes and neither
I hope you can help me