Hi @dunoxx, I am so sorry for the trouble. The n8n Twitter node and the credentials it uses are in urgent need of an update, but unfortunately I do not have any ETA for this right now.
I tried connecting with OAuth1 which previously worked for me (described here), but this now also fails. So I think with the recent changes at Twitter and the overdue updates on our side I don’t have any great suggestion.
It might still be worth re-testing this from time to time though and playing with your exact parameters. @hrsdimitrov appears to have had some success with the generic authentication overe here (so pretty much the thing now failing for me):