How to teach to an adult person that is not used to study? I'm trying to teach some basic things to my mother, such history, basic math and basic physics so she can attend a test.

But because of my mothers personality this has become pretty hard , since she has been influenced from the childhood by sayings  like "I can't study and can't learn", and trash like that.

This is so obnoxious , because to learn a small thing (v.gr.: add fractions) she takes a lot of time (2 or 3 hours) and the next day when trying to recall it, she don't solve the same problems of the day before and she fall in despair and trow out what already learn and stop to study.

I don't think the problem is some kind of disability, I'd rather say she can recall perfect it, but I have seen too that she doubts almost of all the things she knows, and don't write a thing because before she write down something, she believes its wrong!!!

I think too she has a hard time trying to focus on the themes explained.
I have exhausted each idea about trying to explain things: cardboards, games, using the videos of youtube, reading along the books, talking about the themes instead of a serious lecture.

Of course I'm aware I'm not a teacher, but whats does really matter is that she learn a bit of things, that's all.

This is more of pedagogy, but since there is no stack for that I have come here to ask.
Thanks in advance.
Life is dependent many times on being motivated to succeed. There is not a magical formula for having no motivation and yet having success. If your mother cannot find the motivation to learn, it is rather hard to force learning down her throat. If you can make learning matter to her, she will want to learn. 

Perhaps you should look into hiring a professional tutor if your mother needs to learn this material for her employment (or the like). Removing the family element could allow for her to feel more motivation. In certain countries, there are programs for adult learning. One can obtain an equivalent to basic high school education from these programs.