ESP8266 WIFI Connection lost after Acces Point reboot - ide

Question

Heyho,
at first, I am no programmer - it's just my hobby :)
I have a cistern in my garden and I want to measure the level of it with an ESP8266 and an ultrasonic sensor.
I am sending the data via mqtt to my mqtt broker.
Everything working well but when my accesspoint is rebooting two times a day and after that reboot the ESP8266 doesn't connect to the WIFI again.
What I've done so far:
setting the WiFi.setAutoReconnect(true); to true (find that in the Internet)
call the function setup(); in void loop() again
So, I think I have a mistake in thinking with that problem.
Heres my code:
#include <ESP8266WiFi.h>
#include <PubSubClient.h>
#include <Ultrasonic.h>
Ultrasonic ultrasonic(12, 13);
const char* ssid = "XXX"; // Enter your WiFi name
const char* password = "XXX"; // Enter WiFi password
const char* mqttServer = "XXX";
const int mqttPort = 1883;
const char* mqttUser = "XXX";
const char* mqttPassword = "XXX";
#define abstand_topic "home/zisterne/fuellstand"
#define abstand_topic_2 "home/zisterne/mittl_fuellstand"
const int RunningAverageCount = 24; // Anzahl der in den Laufenden-Mettelwert aufgenommenen Messungen
float RunningAverageBuffer[RunningAverageCount];
int NextRunningAverage;
unsigned long previousMillis = 0;
unsigned long interval = 30000;
WiFiClient espClient;
PubSubClient client(espClient);
void setup() {
Serial.begin(115200);
WiFi.begin(ssid, password);
WiFi.setAutoReconnect(true);
WiFi.persistent(true);
while (WiFi.status() != WL_CONNECTED) {
delay(500);
Serial.println("Connecting to WiFi..");
}
Serial.println("Connected to the WiFi network");
client.setServer(mqttServer, mqttPort);
client.setCallback(callback);
while (!client.connected()) {
Serial.println("Connecting to MQTT...");
if (client.connect("ESP8266Client", mqttUser, mqttPassword )) {
Serial.println("connected");
} else {
Serial.print("failed with state ");
Serial.print(client.state());
delay(2000);
}
}
// //Sensor auslesen und übergeben
// int Sensor = ultrasonic.distanceRead();
// char Abstand[10];
// itoa(Sensor,Abstand,10);
//
// Serial.println(ultrasonic.distanceRead());
// client.publish(abstand_topic, Abstand);
}
void callback(char* topic, byte* payload, unsigned int length) {
Serial.print("Message arrived in topic: ");
Serial.println(topic);
Serial.print("Message:");
for (int i = 0; i < length; i++) {
Serial.print((char)payload[i]);
}
Serial.println();
Serial.println("-----------------------");
}
void loop() {
client.loop();
//WLAN Reconnect
if (WiFi.status() != WL_CONNECTED) {
delay(500);
setup();
}
//Sensor auslesen und übergeben
int Sensor = ultrasonic.distanceRead();
char Abstand[10];
itoa(Sensor,Abstand,10);
Serial.println(ultrasonic.distanceRead());
client.publish(abstand_topic, Abstand);
//unsigned long minutes = 1000 * 300;
float RawDistance = ultrasonic.distanceRead();
RunningAverageBuffer[NextRunningAverage++] = RawDistance;
if (NextRunningAverage >= RunningAverageCount)
{
NextRunningAverage = 0;
}
float RunningAverageDistance = 0;
for(int i=0; i< RunningAverageCount; ++i)
{
RunningAverageDistance += RunningAverageBuffer[i];
}
RunningAverageDistance /= RunningAverageCount;
int mittelwert = RunningAverageDistance;
char mittl_Abstand[10];
itoa(mittelwert,mittl_Abstand,10);
client.publish(abstand_topic_2, mittl_Abstand);
delay(5000);
yield();
}
So, now I hope someone of you can help me with my small problem! :)
Greetings,
Philipp