I think the main way to avoid unnatural grammar and expressions is to learn them in context.
This means seeing them used in sentences in articles rather than from a dictionary with simple explanations or even translations.
Additionally, do not learn too many at once, as this can lead to confusion. Learn a few deeply as opposed to trying to learn a bunch at once.
Using passive voice is considered a higher level, however, sometimes it can be difficult for me to write in passive voice.
Does it matter in IELTS writing?
If I use the passive much, can I get a higher score?
If so, how can I improve it?
It will not help much for essay writing.
You only really need it if you are taking the academic test for the port writing.
Map and process tasks need it. Have a look at this link: