Hi, I'm quite new to speedrun and I would like to know how to save states on PC to be able to practice specific points without having to restart the level.

This depends on what game you are running, but most games don't have the ability to make savestates. Some games may have practice mods which you can download, but there is no answer for PC games in general.

thanks, I was quite lost on the subject but thanks for clarifying

It's best to ask this kind of question in the discord or forum for whatever game you are running