ESP8266 not working properly It's the first time I use an ESP8266 and I didn't manage to get a proper response in the Arduino serial monitor. I only see weird characters, when I move the 3.3V wire.

You can see the connections in the following picture:



The code I run is the following one:

#include &lt;SoftwareSerial.h&gt;
SoftwareSerial BT1(3, 2); // RX | TX

void setup()
{
    Serial.begin(115200);
    BT1.begin(115200);
}

void loop()
{
    String B= ".";
    if (BT1.available())
    {
        char c = BT1.read();
        Serial.print(c);
    }
    if (Serial.available())
    {
        char c = Serial.read();
        BT1.print(c);
    }
}


Maybe it's something really stupid. I am a total beginner, so I appreciate any help.

EDIT: I think power supply is 3.3V

SOLUTION: the problem was the power supply. I tried exactly the same using the 3.3V from the arduino instead of the power supply and it works perfectly!
You may well have killed the ESP by supplying it 5v, you have to have a logic level shifter, as Juraj says.

Assuming it's not dead then your next problem is there have been posts about that hardware setup and SoftwareSerial doesn't work at high speed. I can't tell you what it is that doesn't work because turning the speed of the link cures the problem, try 9600 maximum.

[Edited to be less accusational, which was not the original intent]

[Update]

Please see the datasheet here:
https://www.mikrocontroller.net/attachment/231858/0A-ESP8266_Specifications_v4.pdf

The table in section 8.4.4 says that the maximum input voltage is 3.6V
Just after that it says all digital pins are "protected from over-voltage with a snap-back circuit". This snap back voltage is typically 6V.  So does that mean the GPIO are safe up to 6V?

(It might be that this datasheet has been superseded, I am unable to access the EspressIF site at the moment).