Edit Minecraft item?

I wanted to ask how I change the look of items in minecraft. If someone knows and there's maybe a website for it, they can send a link.

You need a TexturePack for this. You can create one https://minecraft.novaskin.me/resourcepacks for yourself.

However, I recommend that you edit the TexturePack with a program (Photoshop, GIMP, …)

This is done using so-called texture packs. To do this, download a default pack from the Internet. You then unzip this and you can change the textures with an image editing program and then insert them into MC yourself