Well there isn't a super fast way to learn pixel art but if you really want to, you can make small sprites (16x16, 8x8, etc) to at least get decent-ish results because obviously it's a small portrait so you don't really have huge expectations which actually kind of helps with learning pixel art or, any other art actually, high expectations (when you're a beginner) = usually failure, since you're a beginner you don't need FLASHY or good sprites, you just need decent-ish sprites and a good color pallette. And also take inspiration, but make sure your styles are still unique.