Need to design the same Desktop program In C , C# (read the details carefully , all bid will be checked)

I have a desktop program but I don't have the source code, I need to do the same program and make it better I need it to be in C / C# as Performance is my priority
I need someone who is expert in C/C# with good communication
it's long term project so Low price will be considered
Start your proposal with C expert to be considered