@kajb1996 do you mind if you first read, you how to avoid delay and use millis()
https://werner.rothschopf.net/microcontroller/202109_millis_two_leds_en.htm
and than how to use this for a simple On/Off Knight Rider LED sequence:
https://werner.rothschopf.net/microcontroller/202109_millis_larson_scanner_en.htm
if you confirm, that you understand the millis() concept, I would show up a PWM sketch also
[even if I'm convinced that something like that gets posted every two months...]