The omissible "that"

[pontios]

Καλό Σαββατοκύριακο.

Just me again.

I have provided 20 sentences below (I thought I could make a single post query this way).
There are a few sentences where I feel "that" could or should be omitted (as they definitely read better), but in some cases it's not clear which way to go, and so I want to get your thoughts.

It was the day that the fascist Italian army invaded Greece.

The disturbing news that Italy had declared war on Greece ....

They asked for whatever foodstuff that he could find at the markets.

He was aware that there were many psoriasis sufferers at the time, and he knew that sulphur could treat the symptoms of this chronic disease.

An acquaintance had told him that a truck was heading that way the following morning.

Let's hope that we're freed from this German occupation soon.

Don’t you know that necessity is the mother of invention?

It was the first time that he had heard Russian being spoken since arriving in Greece.

He made sure that the weight was properly distributed across his horse's back.

Seeing that he lived just across the road, maybe they were starting to get used to him. (Also, no question mark here, right?)

He was surprised to see that there were another two workers employed there.

It was obvious that much progress had been made.

He made sure that she was well rewarded for her effort.

He immediately sensed that they must have suspected him.

He was terrified that some harm would come to his grandpa.

He was convinced that he would end up in prison.

Here's the proof that he was actively serving as a spy.

She read that he was sentenced to twenty years’ imprisonment.

She never ceased to remind him of his all important life mission that she had planned for him.

"You said that you're from Ioannina, right?"

 

[nickel]

Γεια σου, καλημέρα.

First of all, there are two that’s here: First, that used as a relative pronoun. If it is not the subject of the relative clause, it can be removed. It corresponds to Greek ‘που’.

It was the day that the fascist Italian army invaded Greece. (keep, remove, change to ‘when’)
They asked for whatever foodstuff that he could find at the markets. (I’d omit this one, because of 'whatever'.)
It was the first time that he had heard Russian being spoken since arriving in Greece. (keep or remove)
She never ceased to remind him of his all important life mission that she had planned for him. (keep or remove)


In the following sentences ‘that’ is a conjunction introducing a statement. It corresponds to Greek ‘ότι, πως’. There is no problem keeping it. You don’t need to make the text more colloquial, with one exception: “You said you're from Ioannina, right?”

The disturbing news that Italy had declared war on Greece ....
He was aware that there were many psoriasis sufferers at the time, and he knew that sulphur could treat the symptoms of this chronic disease.
An acquaintance had told him that a truck was heading that way the following morning.
Let's hope that we're freed from this German occupation soon.
Don’t you know that necessity is the mother of invention?
He made sure that the weight was properly distributed across his horse's back.
Seeing that he lived just across the road, maybe they were starting to get used to him.
He was surprised to see that there were another two workers employed there.
It was obvious that much progress had been made.
He made sure that she was well rewarded for her effort.
He immediately sensed that they must have suspected him.
He was terrified that some harm would come to his grandpa.
He was convinced that he would end up in prison.
Here's the proof that he was actively serving as a spy.
She read that he was sentenced to twenty years’ imprisonment.
"You said that you're from Ioannina, right?"

 

[pontios]

Thank you, nickel.
Brilliantly explained (I can see how "that" functions now, and I know what to look for through your Greek analogy, που - πως, ότι).

I agree that the last sentence sounds more natural with "that" omitted (as it's dialogue).

 

[pontios]

Ένα επιπλέον ερώτημα.

Τι θα πρέπει να κάνουμε με αυτή την πρόταση που περιέχει δυο "that" (του δεύτερου τύπου);

He noticed that she was carrying a rifle and that she was dressed in a partisan uniform and hat.

Θα πρέπει να απομακρύνουμε ένα από τα "that", όπως π.χ;

He noticed that she was carrying a rifle and was dressed in a partisan uniform and hat.

...ή;

He noticed she was carrying a rifle and that she was dressed in a partisan uniform and hat.