The LangcCorrect web site is amazing.

(1) I'm nitpicking, but "LangCorrect" should be the proper capitalisation.
(2) "Web site" (as two words) isn't wrong, but "website" has evolved to be the more common and more widely accepted spelling.

The benefits of this app is that corrections and reviews are from native people, so they can make valuable suggestions to enhance our knowledge and grammar.

It should be "benefit" and not "benefits", since in this sentence, you only mention one.

However, it can be very frustrating when, despite of writing a lot, we can't write a text as naturally as we would like (to do it).

(1) I'd suggest the addition of a comma, because "despite writing a lot" is a sort of interjection. The comma exists as a pair with the one that comes after "despite writing a lot".
(2) "to do it" isn't wrong, but it can be redundant. For concision, you can consider omitting it if you wish.

This is because we normally are thinking in our mother tongue and we translate literally each word, so we sounds weird.

"We" is plural, so "sounds" should be too.

However, this web site is a great opportunity to interact as much as we can with native people for free and it has no limit of repetitionsn the number of posts you can make.

On the other hand, iIt is a powerful tool for helping people and correcting their texts, because we can interpret and understand how do they order the ideas when they write naturally, so we continue learning while we review their work.

(1) "On the other hand" is used to introduce a contrasting idea. Since there is no such idea here, its use here is inappropriate.

(2) There is a subtle difference between "It is a powerful tool helping people..." and "It is a powerful tool for helping people..." The former focuses on the fact that it IS helping people now, while the latter focuses on the fact that it CAN help people.

(3) interpret: explain the meaning of (information or actions).
"Interpret" doesn't strike me as a very appropriate word to use here.

(4) "how do they" should be used in questions, but your sentence here is a statement.

The Langcorrect web site is amazing.

The benefits of this app is that corrections and reviews are from native people, so they can make valuable suggestions to enhance our knowledge and grammar.

However, it can be very frustrating when despite of writing a lot, we can't write a text as naturally as we would like (to do it.)

This is because we normally are thinking in our mother tongue and we translate literally each word, so we sounds weird.

However, this web site is a great opportunity to interact as much as we can with native people for free and it has no limit of repetiations.

On the other hand, it is a powerful tool helping people and correcting their texts, because we can interpret and understand how do they orderput forth their ideas when they write naturally, so we continue to learning while we review their work.