It looks like this ramp here, in that case it should be better tagged as "highway=footway".
https://www.mapillary.com/app/?pKey=461986184878913

And indeed, @queerthoughts, a connector is missing because it is only connected to a highway area… and those aren’t routable.  So, the solution will probably be something like: add a highway=pedestrian connector across way 517866833 and connect all perpendicular ways to it.

About platform to track C, not sure it is possible to enter trains from the western side.

Really nice if you can do some pictures to confirm what it is like.  If you don’t have time to map the updated situation, I’ll gladly help.