Can't make a chart look the way it should

 Hello!

 I am doing an assignment that says that I should make two axes with the data I have and add a tendency line with R^2 bigger than 0,5 and error bar with standard deviation 0,5. I seem to have the tendency line right, but the error bar is in the way shown only when I make it a fixed value of about 0,20. I also don't know how to make the lines and make the values at the bottom increase by 0,002. I've attached photos of the assignment. The text is irrelevant and in my native language.