The game is somewhat lacking in the documentation/explanation department, so some questions popped up. I hope somebody knows some answers.

1. Passenger Mortality. I have not yet managed to get a train to drive between two stations without at least 3-4 passengers getting "lost", either from age or exhaustion (the game does not specify why they vanish). What do I need to do to prevent that? More waypoints? Adding a layover Station?

2. What exactly do waypoints do?

3. What are the "best" constructs to allow trains to switch between paralell tracks? What about the depot connection?
I was hoping trains could just "jump" tracks in a station (as they can just turn around on the same track). But it appears I have to make those parts (inlcuding signal systems) myself.

4. What exaclty are the 4 Industry Chains? How long are they? When do some of them (like the oil one) start?

5. Where are finished products transported towards? I get that I need to transport the raw material to processing, but where does it go from there?

6. What are the rules for proper track/street crossings, underpasses and overpasses? How much room to i have to plan in for the slopes at both ends? At what angle can street and tracks meet?

7. How much weight (in form of wagons) can I add to a locomotive before it will slow down on a plain? What is the proper weight/KW ratio?

I've only played the game a little bit myself now, so I can answer only a few of these:

1. I was curious about that myself and actual found an answer to that issue on the TF forum. Unfortunately, there's nothing that can be done about on your end. Basically, simulated passengers whose home gets destroyed/redeveloped disappear from the game, and also from your passenger list. From a dev comment it seems tough to change that on their end since the way people are simulated it's an integral part of how the game works. There were musings about "lost" passengers to remain on the list just so you get paid for ferrying them back and forth, but it doesn't appear anything concrete has been done about that.

2./3. I haven't tried this myself yet, but in theory I would think waypoints (as I've seen used in other games in the genre) exist for you to control how your trains travel on a multi-track system, so I would assume you'd have to place one right after a parallel track you want to use branches off. Then add the waypoint to that specific line in between your train's destinations. At least that sounds logical to me. Give it a try. ;)

4./5. I haven't done much with material transportation, but I have a good idea how it works after reading up on it and watching a few videos. I wouldn't call it a industry chain per se. What you see on the map is basically what you get for that game. Bringing raw materials to processing plants will create (increase?) generic products (which are all interchangeable at that point), which then will have to be ferried into cities. There's only a certain demand for each city, which should be shown in their stat list you get by clicking on their names. I'm not exactly sure how much impact if any that has on city development though.

6. Crossings can be tricky. As far as I know, at initial release they were much more headache-inducing. There is no real definite answer for that one. Most of the time it's down to a bit of trial and error to see what the game will let you do and what you thinks works best for you. I haven't tried under/overpasses so, but I'd figure that'd take some experimentation on your part.

Well, that's all I got at the moment. I hope some of that helps.

That helps me a lot, actually.
1. Good to know it is unavoidable.

2/3. You were right. You can add waypoints to the line way. I have been using semi-directional signals for flow control so far, but that is of course much more advanced.
That leaves signals to segment the train tracks for segential use by trains.

4/5. Didn't even knew of the town detail view. I did notice several buildings having a "goods" counter. So I asume demand can grow with the city/growth is dependant on demand being fullfilled.

6. Okay, then it stay with trial and error. It does appear to work a lot better if the crossing segment is a straight peice.

The lost passenger issue is a beloved subject for jokes :) It is a bug and this was detected already under the beta phase. However, it has no impact on revenue.

If a passenger or goods becomes older than the 20min rule, they are taken out of the game. But you get the income from it so it isn't a game breaker, just an odd side effect.

We usually joke that the traveling time is so long that passenger dies before they reach their destination :P