on the arduino pins 20 (SDA) connect to the uvga pin j1-10, pin 21 (SCL) connect to j1-9.
Are we supposed to guess that that is OK? A link to the device you are trying to talk to would be useful?
with the rx/tx communication will work but very slow for my future project.
I doubt that it is serial communication that is the bottleneck. Baud rate, maybe, but not that fact that communication is serial vs. I2C. Hard to say, though, without knowing what you are trying to communicate with.