I2C affect Stepper speed in the main loop

How long does it need for the calls beginContinuous() and distanceContinuous()?

I don't know for how long. The print serial doesnt slow it down
Maybe there is too many write to I2C in the beginContinous then?

Also the distanceContinous has some part use Wire.h which cause I2c hang when I work with it early on.