Hello @jacek_sewerynski,
Welcome to the community! I'd like to help with this issue you are having regarding guardrails in Civil View. The learning channel has this tutorial here that covers this very topic, hopefully you find it useful for this issue. There is also some information here and here that you may find useful. I hope these links are helpful!
Regarding the GEOTIFF maps, you may have to ask in the Civil 3D forums for more information there, I don't know a lot about that particular product. Once you have exported it, I am happy to help with any importing or questions you have regarding that process.
Please hit the "Accept as Solution" button if my post fully solves your issue or answers your question. This lets me know that I was effective in helping you, and thank you for doing so.
Best Regards,