Awesome! Couple of questions:
1. Are those airplanes special built for skydiving? I'm not familiar with them?
At least 3 of them were Shorts Skyvans, built in Belfast, Northern Ireland
Short SC.7 Skyvan - Wikipedia, the free encyclopedia ; they are a STOL twin turbine aircraft, capable of hauling a decent-weighted load, and climb like crazy. The tailgate means you can get a bunch of people out quickly. It's fairly popular in the skydiving community. One of them I didn't recognize.
2. What is the glide ratio of the chutes? she said they need 2 kilometers for all the canopies to open safely?
She's talking about creating enough breakoff separation so that when people start opening their canopies, they reduce the risk of running into each other during the opening sequence when you don't yet have full steering control. That's why you have what's called 'breakoff' which is several seconds before 'opening altitude', where everyone flys away from the center of the formation as fast as they can, called 'tracking'. Once open, you have steering control and can normally avoid other canopies by flying a pre-arranged landing pattern.
3. Are those clouds as solid as you pass through them or can you see the other guys a little?
They can be thin enough for you to see a distance, or so thick you can't see someone 10ft away. Flying thru clouds is not permitted under the FAR's (Federal Aviation Regulations) and a pilot that allows it can lose his ticket. I'm not sure what the Aviation regs in Poland are, but I'll tell you that scared the crap out of me when the nearly completed formation went into the cloud - depending on the altitude you go into it at, and how thick it is, you either need to ride it out until you get below it to breakoff, as breaking off inside of a cloud is extremely dangerous. What really hurts is when they are high/cold enough that they are full of ice crystals...
4. How do you get to be a professional skydiver? Are most of these people ex or active military?
While a lot of skydivers got exposed to the sport thru the military, plenty are civilians all across the spectrum. They just say it and decided they had to do it, found a local dropzone, and committed to learning. "Professional" is a misnomer. You either have to be in the industry, or work for/own a dropzone, or be independently wealthy. Most got in it by seeing it on TV, or making a tandem, and made a decision "I'm GOING to do this".
5. Are there a lot of women in that sport? Where do they come from (military?)
Women are a small but growing segment. Which is why I was so fortunate to meet my future wife skydiving, as there are a) so few women in the sport; b) even less of them are good looking; c) a smaller subset that are single, and, last but not least d) Would actually have anything to do with me - in fact, she swore she wouldn't date a skydiver
6. How physically tough is this sport? Obviously I would need a cargo chute, but is it physically demanding?
I wouldn't say that necessarily. The most physically demanding part about falling out of an airplane is repacking your parachute. But yes, it does take some muscle control to learn to fly, and the adrenaline rush will tach out a newby's heartrate pretty quick.
BTW, if you ever want to make a tandem Arch, 235 is about the max that a tandem master will take - depends on the dropzone.