OK I looked up what xbee S2C are and found this link
a xbee S2C has analog IO-pins. This means a sensor with analog output could be connected to the xbee.
As you wrote that you have very little experience I would like to know what the whole project is.
I guess that a much easier solution to all this can be found.
As you haven't written anything about the physical circumstances I make some assumptions about that:
Distance between Sensor (transmitter) and receiver (ESP8266) 20 m
both transmitter and receiver can be powered by a wallplug permantly:
Solution: using three NodeMCU ESP32 modules. They can be programmend using the Arduino-IDE.
So exact the same programming as with an Arduino.
To NodeMCU-ESP32-module 1 the sensor is connected to an analog input of the nodeMCU
NodeMCU-ESP32-module 1 sends the sensor-data using the ESP-NOW-protocol to
NodeMCU-ESP32-module 2 which receives the sensor-data via the ESP-NOW-protocol and is connected to
NodeMCU-ESP32-module 3 which is connected to NodeMCU-ESP32-module 2 over a serial-connection Tx-Rx Rx-Tx
NodeMCU-ESP32-module 3 is connected to your WLAN to act as the webserver providing the website.
This NodeMCU-ESP32-module 3 is nescessary because ESP32 (and ESP8266) can't communicate to a WLAN and ESP-NOW-protocol at the same time. It could be done by restarting the module some time connected to the WLAN some time connected to the ESP-NOW. But it is easer to have a third one that is connected via serial-interface.
So this solution means only one type of device for all. programmend with the Arduino-IDE
output-power of the ESP32 200mW
bridging a distance of 20-30m inside buildings 80-100 m outside buildings.
additional xBee1-----Arduino for what purpose is this parallel-connection of the XBee1??
connecting the Sensor to the xbee means you have to program the xbee to do the sensor-readings and send them via RF.
How much effort does it take to make a xbee read on an analog input and to send it via RF?
Does there exist an easy to use configuration-software for configuring the xbee or does it requiere a second IDE programming in which language?
With that low knowledge-level just grasping the first ideas that came to your mind is not a good strategy to design such a system
So if you could provide detailed information about the whole thing
what kind of sensor
how many sensor-readings per time-unit
what distance to bridge by RF
what kind of power-supply for both devices (battery or wallplug
integrating your devices into a ZIGbee mesh yes or no
a good suited solution can be suggested.
best regards Stefan