What if i connect bar30 directly to arduino without level shifter
You should use the level shifter, connecting the 3.3V I²C directly in the arduino will damage the sensor.
But, if you are willing to do it, you can use a 10~15KΩ resistor in series with SCL and SDA, this will limit the current and drop the voltage in the end.
It’s working here, but it can damage the sensor. The correct way to go is with the level shifter.
Alternatively, some Arduinos run at 3.3V, I have used plenty of 3.3V Arduinos Pro Mini.
You can get them from Adafruit (If you never used Pro Minis, they need an external FTDI, get those too).
And apparently you can DIY a 3.3V conversion.
While I never encountered or heard of any issues, running the Atmega328 at 16Mhz/3.3V is slightly out of spec, that’s why Adafruit sells them with 8Mhz.