Arduino for STM32

So do I change the prescaler? I already changed the double to uint32. I just copied my example code because the one I wrote is kinda slow? and trying to get duty cycle out of it makes it inaccurate.
Here is my attempt at it

void freq(){
if(true==wave_rise){ // check for second rising edge and ...

Hello, I am trying to make a frequency + duty cycle meter with a graphical display to be added in the future. I am using STM32F1038C8T6 with ArduinoSTM32 core from the github https://github.com/stm32duino.

#include <stm32f1xx_ll_adc.h>

volatile bool wave_rise=false;
unsigned long start=0, first ...