Close rail lines without circle?

[funhave]

How can I connect railway lines, if I have a railway system taht includes head stations and stations with turn around

Can I change existing lines? I think not in an easy way right?

 

[Tecuani]

Can you specify what you mean exactly?

The lines always adjust to the shortest path through the network and automatically update when the simulation is running, but you can of course add and remove stations at any time.
If you want a train to use a specific route then the most trivial way to achieve that is making sure that it is the shortest route to its next station.

Of course it would be nice being able to set additional waypoints that are not stations, for example when wanting to reduce the traffic on certain routes by providing an alternative one.

 

[funhave]

If I start with a line: 1. station (trhough station for beginn-end) set,...2. station set (through station), 3 station (is a through station, but I want, that the train goes back not through the station. after that I go back at the same line and close with the 1. station, but it not possible.

I see the arrows and the path line during building a line, so the tracks are connected and no wrong build

 

[draugrslayer]

No, you don't have to create a loop in the end, just connect the line from station 1-2-3, then back to 2-1 the same route.