I don't know how it's supposed to look on screen so my doubts concern only the written form of the script.
Ok, Magnus and Lasse have the same father and learn about it in the scene 55
but still there are some things I don't quite understand.
"TEEMU (to Lasse): My son.
MAGNUS (surprised): Father!"
Ok he is suprised, it's obvious but:
"LASSE (totally absent): Father?"
What do you mean that he is TOTALLY ABSENT ? Do you mean that the new situation hasn't penetrated yet ?
Maybe be more desriptive, add an action line, that is.
"Magnus who follows the confusing spectacle finally realizes what is really going on."
And indeed the spectacle is so confusing that I'm not sure what Magnus realizes,
why does he say : "Valkaama? ... Valkaama!" ?
Don't you think that a head hitting a stone is an overly used movie trick ?
I think it spoils the whole story ( which is great, btw
Maybe let Teemu start drowning in the lake and the boys try to rescue him but failing.
The father may be able to swim but he's hurt or if it's Scandinavia he just freezes to death ?
That would add some twist and an extra layer to the overall feel of the whole.
Of course it's just one possibility.
And the last thing:
Why do brothers who've recently found each other just part company like that ?
Ok it's your story. These are only suggestions, I hope it was of some help.