After two frustating days (game crashes e.g.) all works fine now. I bought a copy of FO4 at GOG to avoid the downgrade of my steam version but it didn't work very well until I have uninstalled the steam version of FO4 (prob the 2 installations shared some files). My additional mods are: Buffout 4, High FPS Physics Fix and xSE PluginPreloader F4 0.3. Btw. you can avoid the game crash in the train to London: Duck and look to the ground and not out of any window.
