no or not

Remember to capitalize the first word of any sentence. Your choices. He is not a fool. He is no fool.

i always forget that anyway (is capitalizing the first letter so important ?

"He is no fool," is correct.
"He is not fool," is incorrect, a common mistake and very noticeable to a native speaker.

then what about this sentence : it's no true or it's not true

Sawan Codoi always forget that anyway (is capitalizing the first letter so important ?

Yes!
You must also always capitalize the personal pronoun I.

Sawan CodoThen what about this sentence : it's no true or it's not true

"It's not true" would be correct.

Sawan Codothen what about this sentence : it's no true or it's not true

I think until you show the person helping you respect by capitalizing the first letter of each sentence, your questions should go unanswered.

You seem to deliberately ignore the advice you were given.

Repost your question using correct capitalization .

Would you give an explanation why that one is true ?

first i'm not ignoring it deliberately but i'm not familiar or focused with commas or capitalization so be respectful don't judge people by your wrong thoughts you don't even know me

Sawan CodoWould you give an explanation why that one is true ?

1) He is not a fool.
In this sentence, not is an adverb, and it negates the verb "is."
The noun, "fool" requires an article or determiner. The best choice for this sentence is "a," the indefinite article.
Here are examples of positive and nega