if you are named as your grandfather's heir, you can certainly be liable for debts of the deceased
That is true, although you can renounce the inheritance. Surely. you should know the overall balance first.
but when i say I dont want anything, they say "well, will you just make a letter that you renounce then"..
And what if your grandfather was a multi-millionaire?
Why wouldn't they make the court to send an official message to you on the matter?