Writing Feedback / Modern communication have transformed people's time to contact with their friends [4]

There are many grammatical errors and wrong word choices .
I'd suggest you to strengthen your language first before trying to write IELTS essays.
Start with reading as much newspapers as possible and study sentences and structures not single words.

Writing Feedback / Whether a leader is supposed to be young or old should depend on various factors [5]

Avoid using any informal expressions such as " pros and cons", "in a nutshell "

Your position is not consistent throughout the essay, it seems that you start your essay with one-sided opinion approach then end with a balanced- opinion approach :

Your thesis statement says that old is more suitable, while in your conclusion you say that it depends on several factors and the young could be better too in sepecial circumstances.

TRY to read your thesis statement before writing each body paragraph to decide the best matching ideas.

Writing Feedback / High salary or a good work atmosphere. Discursive Essay IELTS [5]

2nd paragraph :
For himself and his family >> use singular they if you talking about someone in general without gender specification
You should say instead :
For themselves and their families.

The same in the following sentences when you are talking about a person
I'd try to avoid this mess and use the pleural form instead ( workers , people ...etc)

In your example , I'd avoid using any fake statistics, this doesn't add anything to your argument. It's a language test not a university essay so try to use precise expressions instead :

Paraphrasing your example >>> the emotional welfare rates has shown" a significant increase" in several studies conducted by ....

Paragraph 3:
The same issue of " him , he"

Writing Feedback / International help for developing countries - what kind of help is the most needed? / IELTS essay [6]

Avoid using there is/are ( there is a large number

Start with others' opinion in paragraph 2 then yours in paragraph 3

Try to use qualifiers to add a strong argument to your point of view and weaken the other side
For example : more / less beneficial
May might could can
Extremely beneficial / might be advantageous .. etc