I was trying to update my lfs to 0,6t version, but now after it I always have an erroe "Can not open file: data\skins\HEL_DEFAULT.jpg"
What the heck?
I'm very sad now

Hel_default is a skin for helmet. Try reinstalling game

I try it before I make this thread
And its not working

Are you sure that you downloaded the full game and not just the 0.6T update ?
Download this one: https://www.lfs.net/file_main.php?id=0

I updated by in game updater
I dont do full game reinstall

I don't know how it has happened but it seems your LFS.exe is running in the wrong location (or part of your installation is missing but that seems less likely). This can happen if the patch is installed in the wrong place, though the installer tries to avoid that possibility.

I would inspect the shortcut to see where your LFS.exe is located, so maybe you can find out what has gone wrong, and you might want to delete the incorrectly installed files if that is the case.

A manual patch installer is available https://www.lfs.net/patch-6t

Or you can go for the full version install, but I'd recommend finding out where your old install is so you can delete it. As Wizard says you may wish to copy some files (setups, skins, etc) in from your old folder if there were some you wanted to keep.

The problem is: that file (HEL_DEFAULT) is missing in your skins_dds folder for the program to start. look for the lost or deleted file (HEL_DEFAULT) and return it to the "skins_dds" folder and it is solved