I haven't found the cause yet.
Somebody help me. Trying to solve the problem since days

here is the sketch:

#include <M5Stack.h>
#include <WiFi.h>
#include <WiFiUDP.h>
#include <NTPClient.h>
#include <Adafruit_Sensor.h>
#include <Adafruit_BME280.h>

#define SEALEVELPRESSURE_HPA (1013.25)

int druck = 1013;
bool flag = false;
int Zahl = 0;
int tdruck;
const char* ssid = "xxxxxxxxx";
const char* password = "yyyyyyyyyyy";
unsigned long delayTime;
float h, t, p;
char temperatureCString[6];
char humidityString[6];
char pressureString[7];
String progno;

hw_timer_t * timer = NULL;
portMUX_TYPE timerMux = portMUX_INITIALIZER_UNLOCKED;

WiFiUDP ntpUDP; //Zeitserver
NTPClient timeClient(ntpUDP,"de.pool.ntp.org",7200,60000);
//NTPClient timeClient(ntpUDP);

Adafruit_BME280 bme;
WiFiServer server(80);
//-----------------------------------------Ab hier keine Netzwerkverbindungen und kein serial.print aufrufen-------------------------------------
void ICACHE_RAM_ATTR getWeather() {
h = bme.readHumidity();
t = bme.readTemperature();
p = bme.readPressure()/100.0;
t = t - 2.3;
p = p + 3.3;
tdruck = int(p);
dtostrf(t, 5, 1, temperatureCString);
dtostrf(h, 5, 1, humidityString);
dtostrf(p, 6, 1, pressureString);
//stunde = timeClient.getHours();
//delay(100); //Ursprünglich 100

if(!flag){
if (tdruck == druck){
   progno = "Konstant";
}
else if (tdruck > druck ){
  progno = "Steigend   ";
}
else { 
  progno = "Fallend";
 }

druck = tdruck;
flag = true;
Zahl++;
dis();

}
}
//----------------------------------------In merker sowenig Anweisungen wie möglich--------------------------------------------------------------
void ICACHE_RAM_ATTR merker(){
flag = false;
getWeather;
}
//-------------------------------------------------------------------------------------------------------------------------------------------------
void dis(){
M5.Lcd.clear();
M5.Lcd.setTextColor(GREEN);
M5.Lcd.setCursor(0, 0);
M5.Lcd.setTextSize(2);
M5.Lcd.println(progno);
M5.Lcd.println();
M5.Lcd.print(pressureString);
M5.Lcd.print(" hPa ");
M5.Lcd.println(Zahl);
M5.Lcd.print(humidityString);
M5.Lcd.println(" % rel. Luftfeuchte");
M5.Lcd.print(temperatureCString);
M5.Lcd.print(" \x60""Celsius" ); // "\x60
}

//-----------------------------------------Hilfsfunktionen---------------------------------------------------------------------------------------
void Say(char x[]){
Serial.println(x);
}

void Say(float x){
Serial.println(x);
}

void Say(char x){
Serial.println(x);
}

void Say(int x){
Serial.println(x);
}
//--------------------------------------------------------------------------------------------------------------------------------------------------

void setup() {
M5.begin();
timer = timerBegin(1, 80, true); // timer 0, MWDT clock period = 12.5 ns * TIMGn_Tx_WDT_CLK_PRESCALE -> 12.5 ns * 80 -> 1000 ns = 1 us, countUp
timerAttachInterrupt(timer, &merker, true); // edge (not level) triggered
timerAlarmWrite(timer, 1000000 * 60, true); // 1000000 * 1 us = 1 s, autoreload true
timerAlarmEnable(timer); // enable

IPAddress ip(192, 168, 0, 5);
IPAddress gateway(192, 168, 0, 1);
IPAddress subnet(255, 255, 255, 0);
IPAddress dns(192, 168, 0, 1);
//IPAddress pdns(8,8,4,4); option

WiFi.config(ip,gateway,subnet,dns);// WiFi.config(ip,gateway,subnet,dns,pdns);

Serial.println(F("BME280 test"));
bool status;
status = bme.begin(0x76);

// Connect to WiFi network
Serial.println();
Serial.println();
Serial.print("Connecting to ");
Serial.println(ssid);

WiFi.mode(WIFI_STA);

WiFi.begin(ssid, password);

while (WiFi.status() != WL_CONNECTED) {
delay(500);
Serial.print(".");
}
Serial.println("");
Serial.println("WiFi connected");

// Start the server
server.begin();
Serial.println("Server started");
delay(10);

// Print the IP address
Serial.println(WiFi.localIP());

timeClient.begin(); // Zeitserver
timeClient.update();
Serial.println(timeClient.getFormattedTime());
}

void loop() {
WiFiClient client = server.available();
if (client) {
Serial.println("New client");
// delay(1000);
// bolean to locate when the http request ends
boolean blank_line = true;
while (client.connected()) {
if (client.available()) {
char c = client.read();
if (c == '\n' && blank_line) {
timeClient.update(); //Zeitserver
getWeather();
client.println("HTTP/1.1 200 OK");
client.println("Content-Type: text/html");
client.println("Connection: close");
client.println();
// your actual web page that displays temperature
client.println("<!DOCTYPE HTML>");
client.println("<html>");
client.println("<head><META HTTP-EQUIV="refresh" CONTENT="15"></head>");
client.println("<body><h1>        Zimmertemperatur</h1>");
client.println("<table border=10 bordercolor=#4844EC width= 40% cellpadding=10><tbody><tr bgcolor=#CCFFFF><td>");
client.println("<h3>Zeit ");
client.print(timeClient.getFormattedTime());
client.println("<h3>");
client.println("<h3>Temperatur  =  ");
client.println(temperatureCString);
client.println("°C</h3><h3>Luftfeuchte  = ");
client.println(humidityString);
client.println("%</h3>");
client.println("<h3>Luftdruck     = ");
client.println(pressureString);
client.println("hPa<h3>");
client.println("<h3>Tendenz  &nbsp     = ");
client.println(progno);
client.println(Zahl);
client.println("</h3></td></tr></tbody></table></body></html>");
break;
}
if (c == '\n') {
// when starts reading a new line
blank_line = true;
}
else if (c != '\r') {
// when finds a character on the current line
blank_line = false;
}
}
}
// closing the client connection
delay(3);
client.stop();
// digitalWrite(14, LOW);
Serial.println("Client disconnected.");
dis();
//M5.update();
}

}