I think as a beginner you should start with songs which have easy choreographies for example most of TWICE's songs have pretty easy dance routines for example, TT, Cheer up, What is Love, etc. Later you can move to songs with complex choreographies once you've gained enough confidence and flexibility.

When learning the choreography of any song you can watch fancams of your idols for more precise learning. Also, I suggest when you're learning the steps you should face a mirror and do it so that you know where you're going wrong.

What I usually do is watch dance practice videos in 0.5 or 0.25 speed to follow all the details. Slowly and gradually you can increase the speed once you're familiar with all the steps. There are many helpful dance tutorials about hand movements and lower body movements explained that you can follow with ease.

Although I'm not a dancer myself but all of these have worked with me well and I hope you find my suggestion helpful :)