How do I set the ESP8266 to AP mode for WiFi network selection on first startup?

Hello, I have a problem. I have created my own weather station with a temperature sensor and a particulate matter sensor, the data is sent to a ThingSpeak server and to a web server where the data is displayed. But I am looking for a way to make the module work in AP mode when I first start it up and to be able to select the WiFi network. Unfortunately the tutorials and examples from the internet are very complicated, I need the simplest one that exists. I used this guide:
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Everything here works but I am having a hard time linking it to my application. Maybe someone can explain it to me "in a spatial manner".

Greetings

This is how I would like the network scan to be performed. I would like the selection to be at the beginning and then my page to be done. I know it's a mess out there, I'm a beginner. Please advise

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I will try to play with this feature tomorrow. Thanks for the advice tomorrow I will share what I manage to create

Added after 10 [hours] 36 [minutes]:

I have reviewed this scan function, and it is great only I have one question. I search for a network and it finds me a network xxx I want to connect to it and after connecting it starts the web server. And how to do a simple network selection and password.

Here is a tutorial on how to use the WIFI MANAGER library for ESP Link .
Alternatively there is the FSBrowser NG project Link . The HTML local page is saved in regular HTML files. You need to have a file system upload plugin added to the ESP, this makes sense for flash larger than 1MB. Example you compile for FS (SPIFFS) at least 128kB (no larger than the contents of the DATA directory), upload firmware, upload web page files separately:
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Within the example is a set of sample files, if you save the example AS, there is a DATA folder added in its directory, inside are sample HTML files - WIFI configuration, adding a password, updating firmware from a browser, etc. bits and pieces:
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The first time you start up, you connect to the module set to AP+ST mode, go to 192.168.4.1/admin, then from the network settings menu and select the network parameters as if you were using a smartphone:
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Edit: 192.168.4.1 of course.

Esp8266 nodemcu v3 . I'll be back from work trying to get something working.

Added after 6 [hours] 28 [minutes]: .

I succeeded with the help of WiFi manager. Only I have 2 problems still Well, in the program code in setup() I use the following settings:
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And unfortunately after every unplugging it loses the given network. How do I solve this? The second thing I would like to do is to impose a fixed ip on the device after connecting to the network, e.g. : 192.168.1.10 , I seem to have this defined at the beginning but it takes a different ip:

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Please advise and thank you already for any help.

Well rather wifiManager.resetSettings(); should be commented out.

But if it is not there then automatically when I leave the "known network" then my device will be the AP? Do I understand this correctly?

In the example it is commented out, this is used to reset the settings. If, for example, you change the wifi password and the program goes dumb, or for some other reason you want to connect to another network you can assign this function to a button - e.g. you press the button after IO13 for 5s, as a reaction you call the function wifiManager.resetSettings(); and reset the WIFI settings - it starts up again as an AP and no network is entered.
As you've added it to setup it does a cleanup of your WIFI settings after each reset, as expected.
And you can let go of those manual settings for IP, Gate, etc., from the library description it appears that this is configured and stored in EEPROM (emulated).

Ok. But how can I no longer connect the button? Any idea how to use this function?

If it doesn't find the network or you change the password it starts up in AP mode and you can log in from your smartphone to change the SSID and password. That's probably enough for you, but there are many other options, I haven't tested them, there are quite a few descriptions in the examples and on the library page.