[lugerholsterrepair]

The gun is a Mitchell luger made in 1991 ...This is likely not the only part you will have trouble with.
It is my thinking that these pistols are not always interchangeable with original Luger parts.
I suspect the spring. It is, after all, what holds the extractor in the down position.
The extractor should move freely in the extractor slot in the bolt.

Do you think I could polish the sides of the extractor with my dremel tool?
No, the extractor has flat sides and a wheel could cause a wavy side. I would take John's suggestion a little further and polish the sides on a flat surface with very fine black sandpaper untill it moves freely.

Then with bolt in hand see if the spring is forceful enough to move it into the proper position. If not..gently stretch it out a bit.

Jerry Burney