Some tutorial videos suggested use of potentiometers to reduce vdc output…
Since the unit produced the correct voltage before you created the short circuit, there is now obviously a defect within the unit. A potentiometer will not remedy this defect.
You need to identify the defect component(s), then replace them. The link in @bertus
' post #4 seems to contain some good information for troubleshooting - judging by the toc.
You miss manors inside this community..
sometimes may be very direct, I can see no lack of manners in his replies.
Before criticizing others, give some thought as to what they ask or recommend and why that might be so. Contrary to you, those who have responded so far have quite a history on this platform. We're constantly experiencing new members with little knowledge who in Bluejet's words want the "shortcut route to knowledge" - or simply the "shortcut route" without achieving knowledge.
Lack of knowledge can be dangerous, even lethal when it comes to mains powered components (or even low voltage but high power components). This is when and why we recommend extreme caution or even to refrain from trying to perform a repair by the uninitiated.
Of course one needs to learn to get out of that hole into the realms of the knowledgeable. But dangerous voltages or current are not the best way to achieve that. Imho it is better to do such work under direct guidance of someone experienced who can prevent that you make possibly deadly mistakes.