Is there a way to change resolution of videos from 1080p to 480p ?

I have many videos in 1080p or 720p and they take up so much space plus the video is jittery. My laptop has a slow processor and sometimes the laptop warms up, even overheats and shuts down.

I'd like to get videos down to 480p so they will be more smoother playing.

Is there a program or website where I can change the resolution of my videos down to 480p ?

There are many converters which can do this. The free VLC Player will do it, but their interface is not always user-friendly. A set of instructions for it is at https://www.vlchelp.com/convert-video-format/ XMediaRecode can do it to, but is also not the most user-friendly: https://www.xmedia-recode.de/en/

Mac might have built-in software to do this. I have not used Windows Media Player in so long that I cannot tell you if it has this function.