ARDUINputOutput:
In particular, when I run https://github.com/jrowberg/i2cdevlib/blob/master/Arduino/MPU6050/Examples/MPU6050_raw/MPU6050_raw.ino the Serial Port Monitor outputs strange, incomprehensible symbols.Here is a sample:
Look in the bottom right of your serial monitor, where the speed is 9600. Now look a the sketch you referenced:
Serial.begin(38400);
So, set your serial monitor to 38400.