Blender only masks the outline of what I'm trying to mask I am still very new to Blender Stack Exchange so if I deviate from the format that is because I don't really know this.
Problem:
When I mask out something (in this case, an arm), it only masks the outline and doesn't fill it in. Here is some images of the problem:

ps: I am still learning the basics of masking so it is a bit bad of a mask...

I hope someone can help me with this and maybe the format of this website a bit.
Ok, so it turns out that the direction of the mask was flipped. Selecting the mask and switching the direction fixed the problem.
For some reason I had this problem again and this didn't work. Maybe there are different ways to solve different problems with the same look or something, I don't know, its weird.