Df player mini, can any one help me

You seem to have changed the code from:
DFRobotDFPlayerMini mp3(8, 9);
to
DFPlayerError mp3(8,9);

Is that because you got the error I got?

sketch_aug28b:4:29: error: no matching function for call to 'DFRobotDFPlayerMini::DFRobotDFPlayerMini(int, int)'
 DFRobotDFPlayerMini mp3(8, 9);
                             ^

Looks like you are creating the DFPlayer object incorrectly. This is how it is done in the "GetStarted" example from the DFPlayer library.

#include "Arduino.h"
#include "SoftwareSerial.h"
#include "DFRobotDFPlayerMini.h"

SoftwareSerial mySoftwareSerial(10, 11); // RX, TX
DFRobotDFPlayerMini myDFPlayer;
void printDetail(uint8_t type, int value);

void setup()
{
  mySoftwareSerial.begin(9600);
  Serial.begin(115200);
  
  Serial.println();
  Serial.println(F("DFRobot DFPlayer Mini Demo"));
  Serial.println(F("Initializing DFPlayer ... (May take 3~5 seconds)"));
  
  if (!myDFPlayer.begin(mySoftwareSerial)) {  //Use softwareSerial to communicate with mp3.
    Serial.println(F("Unable to begin:"));
    Serial.println(F("1.Please recheck the connection!"));
    Serial.println(F("2.Please insert the SD card!"));
    while(true){
      delay(0); // Code to compatible with ESP8266 watch dog.
    }
  }
  Serial.println(F("DFPlayer Mini online."));
  
  myDFPlayer.volume(10);  //Set volume value. From 0 to 30
  myDFPlayer.play(1);  //Play the first mp3
}