The Matrix is finally working. 'Only' four LEDs needed to be replaced before the whole string was working. Early testing Firmware is running! I also used PlatformIO and Visual Studio Code which was surprisingly nice and fast to work with.

Files are also now on gitHub: https://github.com/tinyledmatrix/reDOT_RGB

Will shoot some more nice Images now an post them

There is still much to do - for example all the i2c stuff. But the current state show that the most important part the LED Matrix is working.