two functions at once

Yes, Arduino added the boolean keyword as a synonym of bool, probably to be closer from Processing language (unsure of that), but both work. You can write boolean instead if you prefer, it will be exactly the same.

my code lacks something important, OMG I'm stupid ^^ :

        if (millis()>(lastLed1Blink+led1Delay) { 
            /* Add code to make led1 blink */ 
            lastLed1Blink=millis()
        }

        if (millis()>(lastLed2Blink+led2Delay) { 
            /* Add code to make led2 blink */ 
            lastLed2Blink=millis()
        }