RE the picture: That's a really dull tooth IMO. There's absolutely no corner on it and the top plate is a mess.
No worries though, you just have to file more. It looks like you have good angles with the file, don't change that. Don't bother with a guide if you don't feel you need one. Just keep filing back until you see metal coming off the corner AND the top plate is sharp. Sometimes that happens at the same time, other times one comes before the other. You need both.
Don't be afraid to take off material. Don't be afraid to screw it up. Don't be afraid to screw up a chain on your way to learning to sharpen.
No worries though, you just have to file more. It looks like you have good angles with the file, don't change that. Don't bother with a guide if you don't feel you need one. Just keep filing back until you see metal coming off the corner AND the top plate is sharp. Sometimes that happens at the same time, other times one comes before the other. You need both.
Don't be afraid to take off material. Don't be afraid to screw it up. Don't be afraid to screw up a chain on your way to learning to sharpen.