don't get how it works

[propovednick]

After almost a hundred of hours I thought I know how train signals work, but now I'm not sure. Here is my train and it stuck.

fac.png (3.86 MiB) Viewed 1302 times

I don't understand. It stopped on chain blue light. But the next two railroad sections on its way are free...

[Loewchen]

You have a chain of chain signals that ends at an occupied block, so no train trying to path to that location can enter any of those chain signal blocks until the rail signal block is free.

[propovednick]

got it after some experiment, another question: why trains ignore buffer path when it has a station?

[Nidan]

got it after some experiment, another question: why trains ignore buffer path when it has a station?

In your screenshot it'll go there after about 5 minutes.
Stations have a much higher penalty to the train's pathfinder than waiting for another train to be able to continue it's own journey. Reason might be that (potentially) blocking a station is considered worse than waiting on open track (often only waiting for a short moment until an intersection is clear).

Details can be found on the wiki: https://wiki.factorio.com/Railway/Train_path_finding