troubles using the pencil

Help quest

I have 2 troubles using the pencil while drawing.

1. 1. The line does not appear at the moment the pencil touches the surface, only after a while. In this case the line is not accurate and it is very difficult to draw like this
2. when I paint a stain of some color, red for example, and I draw over it with a pencil with the same red, the color of the pencil line is not red as expected, but darker or lighter. So, if I want to draw a  red line starting the red stain , and to be sure- put the pencil over this stain to begin there, I receive a line not the same color.

It is very annoying. 

What can I do to remove these problems?

Thanks

Ruth