hHello every one , iI'm new here .

Sentences start with capital letters. The pronoun 'I' is also capitalized whenever you write it.

I don't know what to say and i I'm a programmer .

The correct spelling is 'programmer'. Once again, always capitalize the pronoun 'I'. When you make contractions and the apostrophe ( ' ) is in the middle of the contraction, there should not be any space before or after it.

sSo iI use the famous words " hello world " to say hello to all of you.

Once again, capitalize beginnings of sentences and the pronoun 'I'.

And iI'm poor in eEnglish, so it's hartd to write a long sentence.

Don't begin sentences with 'and'. The word 'and' is used to join to sentences together into 1 big sentence.
In English, if you talk about 1 thing (a sentence), always use the articles 'a' or 'an', depending on if the thing starts with a vowel sound.
You could also not use 'a' or 'an' and change your sentence to talk about many things.

tThanks for correcting my sentence.

When a verb (an action word, any word used to describe something you do) comes after prepositions like 'for', 'after', 'before', etc, you should use the infinitive form (the form with the '-ing' ending).

hHello every one , iI'm new here .

I'm a programer and I don't know what else to say and i 'm a programer .

sSo i use the famous wordsn order to greet you guys, I will use " hello world " to say hello to all of you." as it's a very famous phrase within programming.

And iI'm poor in ebad at English, so it's hartd to write a long sentence.

tThanks for correcting my sentence.