It is not my understanding of the terms that is the problem - it is yours.
As I noted earlier (several times, I believe), there is some confusion about the terms but they have quite specific meanings - as the various sources I've mentioned state.
But to simplify things: A weekly drop in inflation is negative inflation, i.e., falling prices over a short period.
Negative inflation is often caused by a sharp drop in the price of certain goods or services - in the case of Russia, apparently food prices.
Negative inflation is a general price decrease that is not sustainable.
This is a temporary decrease that is part of a general trend of rising prices.
Over the medium to long term, that is called deflation.
The term deflation is used if the decline occurs over 3 consecutive quarters (so the general price trend is downward) or by some economists if the inflation rate is zero (the late Nobel Prize-winning US economist Milton Friedman was an advocate of zero inflation in monetary policy).
Weekly fluctuations are, therefore, negative inflation.
That is why, for example, there can be headlines like "Russia seen holding rates at 7.5% until year-end as inflation remains elevated" (https://www.reuters.com/markets/euro...ed-2022-09-30/), and why, in September 2022, the inflation rate in Russia reached 13.7 percent relative to the corresponding period of the previous year.
So, to put it simply, weekly downward fluctuations in inflation rates do not constitute deflation but are negative inflation if there is still an inflation rate about zero percent.
However, you can nourish your illusions by more insulting posts if you wish but I will not dignify them with a response,