"I am thinking about, what it can do to oneself."
Translation:Jeg tænker på, hvad det kan gøre ved én.
This sentence would make much more sense in English with 'you' instead of 'oneself'. Anyway I don't think anyone younger than 80 still says oneself!
This makes no sense in English because the "oneself" needs a "one", which doesn't exist here, and in any case "it" is the subject of that clause, so the only thing that could be -self'd would be "itself".
I'm not 100% sure but I think the ved goes with gøre rather than en. So 'gøre ved' means 'do to' and then you could have any object where 'en' is.