Yes, it looks like the second code you wrote.
I have a drawAll method that draws everything, first the grids, then all tracks (a number is actually a track, so it paints a number and all of his lines and dots and then go to the next number).

So I should set the map image as the form background and paint the grids on the form, and then the painting will be on the transparent panel ?

My map isn't rotating or scaling, it's static, and the grids are too, so I only need to redraw everything when the user inserts a coordinate and a number, but it happens 6-12 times in a minute, I don't want the program to repaint the whole lines and dots because the amount will be very high in some point (about 50 lines) and repainting 50 lines every 5 seconds will be hard. I want a different painting block for each number and its lines, can I create...

Here's an example:
A user type number 12 and grid 34 so the program paints a point in grid 34 with the number 12 (the program uses a dictionary and stacks to store it), then, the user inserts the number 12 again but now grid 35 so the program paints a dot in 35 and connects it with a line to the previous dot. Lets say that a few more dots and lines are painted and now the user inserts a number with grid zero which means he want to remove the...

In my program, the background is a map, and the map has 100 grids on it.. the user inserts coordinates and a number and the program paints a dot in the coordinates provided by the user, if the user inserts another coordinates with the same number provided earlier, the program paints another dot and connects the previous one with the new one.

A few users will insert coordinates so the program will be a bit busy painting all the lines...