I'm basically new to coding, right now I'm studying web design at university and they gave us this homework where we have to create a website like youtube with a large amount of videos +200 (idk why it couldn't be 10 videos)

Right now I'm facing this problem of thumbnails, I really want it to look good, and have responsive thumbnails such as youtube, where you can put the mouse over the video's thumbnail and it will play a part of it.

I'm using for videos, and for the right-bar how could I place the videos thumbnails as I said before. Since it will be a large amount of videos I don't feel like making a gif, or a personalized video for each video, is there a way I can automate this?