Remove line from shape

Question 1

I need to remove line from shape, but when I use pathfinder tool, it makes shape from my line(Arc tool), then removes it.

How to remove only line itself?

These are my lines, I want them to cut through the circle:

This is what happens when I use pathfinder and delete the shapes, (it adds in extra space)

Question 2

You want to select all the lines and Expand them.

Go to Object → Expand, you only need to select Stroke.

This will convert your strokes to paths (fixing that mistake which is caused by the computer auto selecting an area to fill)

Then you can use the Pathfinder (Window → Pathfinder or Ctrl/Command+Shift+F9) to cut them through.

You can also do Object → Path → Outline Stroke which does the same thing (in your scenario)

Answer