Could you please help me to fix it? Do you have any idea of how I can solve it? Could your code help me to do it?
You'd be very helpful, really
are you able to show those characters on the serial monitor, when put into a string? (not from twitter, but when you just do Serial.print("those special characters"); ?
You can replace those ñ , ¿, ¡ with the actual character. I did that in another project of mine (www.jo3ri.be/arduino/projects/castduino). You can start looking for &# with Textfinder and when found replace those with along with the according number.
Something like if &# and 241 than you have ñ.
also check google on "string replace" (http://www.cplusplus.com/reference/string/string/replace/)