How do the U Boat torpedo men raise the torpedoes into the tubes?

In the rear since there were two tubes, the extra torpedoes sat on rollers behind and in line with the tubes.

Yes, it is via a series of overhead rails, winches, and pulleys. You can see some of it in action here on this German WWII Newsreal footage

https://www.youtube.com/watch?v=5K8L3VH-gu8

EDIT- video embeds are still a no go in the "upgrade"...

If you look at the photo that I think you mean, there are winches that raise and lower the rail, above it and connected to the crosswise traveler beams. The rail to weapon attachment is a fixed one.