Do any of the sites that cover idioms work for you?
It is helpful for us to know if you can't access the sites that review/discuss English-language idioms as it explains, in part, why you're having such difficulty with them.
I'm not sure how you're supposed to do your work if you're not allowed to access resources that would increase your ability to do that work effectively.
There are many jokes in North America about the odd descriptions of things coming from your country. I'm surprised the government doesn't put more effort into letting people learn English as it is actually used.