how could I improve my writing for IELTS.
I think I know the answer to this question! Google around about this: critical thinking, logical fallacies
If you get very good at critical thinking, you will be able to do well with whatever essay prompt you see. For a good book, google this: critical thinking, , nosich, asking the right questions
...should help by allowing high levels
...seek asylum in developed countries. ----I don't think you need to write "overdeveloped."
Do not capitalize unless it is the first word of the sentence or a proper noun:
host countries also receive...
However, it is argued that it is not an open and shut case... people to other forms of crime and corruption.----It is good that you used this paragraph to talk about the other point of view. However, at the end of this paragraph you should tell why your opinion is still more accurate than this opinion.
To sum up it is
clear that for host countries, refugee migration is not only something that creates few problems but also an opportunity for them to gain the support they need to survive.
I don't know how the test is scored or if you can get a 7, but I think your writing is at a very high level with just a few mistakes. Keep practicing!