Serial protocol sender reader lost data

I want to communicate 2 arduino Megas by multiserial protocol,
when I send the byte 49 (number 1) I recive another data on my Serialport
please, how could I fix this issue?
Should I better use the library softwareserial?
I need to use Serial comunication for this project due to I don´t want to pay much money

enviar2.0.ino (229 Bytes)

recibir2.0.ino (254 Bytes)

There is no need to use SoftwareSerial with a Mega which has 3 spare hardware serial ports.

Start by just using Serial.print() and use only human readable characters. When you have that working you can consider more complex stuff if you need it.

What line-ending have you selected in the Serial Monitor. Unless you have it se to No line ending it will be sending more than one character.

Have a look at the examples in Serial Input Basics - simple reliable ways to receive data.