If you can visit a library, some great places to start are Understanding Comics and Making Comics (2 separate books) by Scott McCloud, and Drawing Words and Writing Pictures and Mastering Comics: Drawing Words and Writing Pictures Continued (also 2 separate books) by Jessica Abel and Matt Madden.
Hello i wanna try to practice on that but i don't know how it works. ( and saddly i can't afford books OTL" I'm more looking for deviantart,tumblr or youtube videos. )
It's especially in terms of creation and positions of the panels and angles of view of characters that I don't understand much saddly.
If you don't mind audio-only advices, I've been listening to this podcast series that discusses a lot of helpful stuff about (web)comic creation, you're free to choose which topic interest you the most. They're quite long so you might wanna hear them when you're doing another thing or while on the go. (They also mostly focus on the writing or process aspect but still worth recommending!)
Other than that, I'll see if I can dig up any past tutorials I saved. I never did one myself but I do look up a loooot of tutorials myself to get prepared. (And I'll follow this thread too for tutorials I haven't seen before.) :0
Comic tuts | Perspective tuts | Composition tuts | Storyboarding tuts
Be sure to give yourself a regular goal for completion, and make a backlog before you start posting, in case something happens. Good luck!