In order to get independence in the tasks, I followed the hint of "blink without delay"
a johnwasser code example "DaftPunkLights"
https://forum.arduino.cc/index.php?topic=105210.msg789378#msg789378
another code example
► libraries
and I found some dedicated libraries
neopixel adafruit GitHub - adafruit/Adafruit_NeoPixel: Arduino library for controlling single-wire LED pixels (NeoPixel, WS2812, etc.)
and tutorial Deconstructing the Loop | Multi-tasking the Arduino - Part 3 | Adafruit Learning System
FastLEd
Arduino Light Animation (ALA)