Question for panzer campaign stalingrad

[Sharky]

The company sized unit should be able to at least hold the 300 man unit off for a bit until you can get units up to help stem the tide.

so basically i should send as many unit from the city to the north for the time being ? tried again to assault but nothing at all, 1 killed in soviet side and that's it

one thing i don't get is rail mode. on another game i cannot put some unit on rail. they have full movement point and some others are already on rail. apparently there's a limit, but can't see it anywhere. the website say to go to parameter data but can't find it. at first a thaugh could not go on rail in forest hex but even in open country appear not to work. any tips ?