Ok..
About the Voltage, i need to add some ics, because the data is transfered by K-Line.. It is not problematic...
But i dont know if the sketch work.
I put a serial read of both serials in loop an than a print command... Is the arduino fast enough to write every single bit or i need to write first into ram? I think it sounds a litlebit strange, but im new here 
Later i post the sketch i have made...