it's almost as if you've never heard of personal heaters. The whole "installation" and "refitting" process is this: buy one in any store, come home, plug it in in the grid. Wow, so hard, so expensive.
The German government doesn't even have to pay for them (individual households buy them, not the government), it would just need to increase the electricity output - exactly where nuclear plants would be useful.
That temp change just sounds like a slight increase duw to the ambinet room heating up. Please sort your heating out straight away.
That heating fan you mentioned, is that one of those electric room rans? like this? https://www.amazon.com/Electric-Heaters-Portable-Thermostat-Heating/dp/B0895QVCYC If so, do not use that for heating the tank. This is meant for room heating, not for reptiles.