In writing task 1 the examiner will assess your answer in four areas:
Coherence and cohesion
Numbers 2-4 depend mostly on your level of English.
Number 1, Task Achievement, depends more on knowing how to answer the question.
It's possible to have very good English and fail to get the score you need because you don't know how to answer the question.
To get a 7 or more for Task Achievement, you need to:
Provide an overview.
Write about the key features and other details.