In 2018, including athe winter season, the number of influenza 's victims in Japan was around 3,500, and for whom the immediate cause of death was the influenza virus.

To date, there have been approximately 3500 deaths due to the coronavirus inacross two winter seasons.

"In" is not wrong, "across" just feels more natural. Your English is extremely good, so I'm being picky with corrections because you are at a high level.

In fact, that figure includes not only the immediate cause of death due to a coronavirus, but also the death of as by chronic disease causexacerbated by the corona virus.

Exacerbated = 悪化した

Given that weIf we (were to) add the number of relative death causes of chronic disease such as a hypertension and a diabetes, etc.

caused by Influenza to the number of the immediate cause of deaths caused only by influenza, the total number of the deaths caused by Influenza in Japan should be more than ten thousand people for a season in general.

We have been wrapped in aengulfed by lies and ignorance.

More poetic. Your original sentence is grammatically correct but doesn't sound natural.

However, I think he's always made aking speeches based on illogical thinking, or on playing to party politics.

His counter measure abouts for coronavirus wasere too late and sluggish.

There seem to be no close aides beside of him to advise and he cannot grabsp the present situation at all.

"Grasp" is often used for 'understand' or 'comprehend.'
While 'Grab' is a synonym for 'grasp', 'grab' is not used for 'understand' in English.

This is the only last chance that he has to do, if he can't do now, it's now or never.

I am sure that his party will lose at the next election, and cannot buthe will be forced resign atfter the next election for sure or he might be destined to be fired byefore the next election willeven begins.

In 2018, including a winter season, the number of influenza 's victims in Japan was around 3,500, and the immediate cause of death the influenza virunot including deaths caused by complications or underlying issues.

There's not a word for what I think you're trying to say. For example, if I get cancer and die, I can "die from cancer," or, if I get cancer, already have asthma, and can't breathe, I "die from complications" or "die from other underlying issues." I hope that difference makes sense, even if it's gruesome.

To date, there have been approximately 3500 deaths due to the cCoronavirus in two winter seasons.

In fact, thatis figure includes not only the immediate cause of death due to a coronavirus, but also the death of a chronic disease caused by corona virudeaths directly caused by the Coronavirus, but also deaths related to resulting chronic diseases.

G, given that we addinclude the number of relative death causes ofdeaths related to chronic disease, such as a hypertension and a diabetes, etc., to this figure.

caused by Influenza toConsidering the number of the immediate cause of death causdeaths related byto influenza, the total number of the deaths caused by Influenza in Japan should be more than ten thousand people for a season in general.

I chose "related to" here, but, depending what you mean, you can also say "caused by" with slightly different meaning:
caused by= just influenza
related to= influenza+ other lasting problems

We have been wrapped in a lies and ignorance.

We have to be more careful about thisese kind of statistics.

Note that kind is singular, but because statistics is plural, we use "these"

I'm sure that even the prime minister of Japan, Suga, is sure to know this fact.

However, I think he's always made a speeches based on illogical thinking or on playing party politics.

Or he's a just fool or an ignorant man.

You always want things joined by "and" to be the same part of speech.
You could also say "Or he's just foolish or ignorant" (both adjectives)

His counter measure about cCoronavirus was too late and sluggish.

There seem to be no close aides beside of him to advise, and he cannot grabcontrol the present situation at all.

He seems to be in totally confusioned.

There is no time for him to think it over, h. He had better act now or he'll miss the busoat.

I don't know how often English speakers are taking boats places, but for some reason the expression is "to miss the boat"!

This is the only last chance that he has to do, if he can't do, so he must act now.

I'm not sure what you meant originally. It can't be his last chance if he's not doing anything?

I am sure that his party will lose at the next election, and. He cannot but resign at the next election for sure, or he might be destined to be fired by the time the next election will begins.

It's best to try and only have two clauses (subject+main verb) per sentence in English. Your original had three, so I broke it into two sentences.