Hi Aiden,

Your written English is very good and your examples fundamentally all work for me.

I have some minor comments below:

Could you check these sentences please?

I've just learnt some idioms here https://www.italki.com/article/778/The-Most-Useful-English-Business-Idioms by Jack Davidson, and I'd like to put them into practice.



Back to the drawing board: It's such a shame that the plan didn't work. I'm afraid we'll have to go back to the drawing board and think about introducing foreign workers again.



Ballpark figure: He didn't do any further research before the conference, and it's so irresponsible of him to just throw some ballpark figures at us.



To be on the same page: How capricious surprising that he is to fired up at my proposal this morning! I thought we were on the same page after we went for a drink in a pub last night.



To be up to scratch: People who have stayed at schools and studied for years are usually not up to scratch for the modern corporate world.



The big picture: This investment plan might seem ineffective in the moment, but if you look at the big picture it can earn you a wealth  lot of money when you retire.



Blue collar: There's no shame on being a blue collar worker since you make money on your own.
or perhaps  There's no shame about being a blue collar worker, they are actually very important. The company can't function without them.


By the book: We are told to be a good kids at schools, but the corporate world doesn't function by the book.



There are still many of them on that link. Thanks for taking the time. Corrections and feedback are appreciated.

Could you check these sentences please?

I've just learnt some idioms here https://www.italki.com/article/778/The-Most-Useful-English-Business-Idioms by Jack Davidson, and I'd like to put them into practice.



Back to the drawing board: It's such a shame that the plan didn't work. I'm afraid we'll have to go back to the drawing board and think about introducing foreign workers again.



Ballpark figure: He didn't do any further research before the conference, and it's so irresponsible of him to just throw some ballpark figures at us.



To be on the same page: How capricious he is to laugh at my proposal this morning! I thought we were on the same page after we went for a drink in a pub last night.

"How capricious he is to dismiss my proposal this morning! I thought we were on the same page after we went for a drink in a pub last night."

How capricious he is to fire me this morning! I thought we were on the same page after we went for a drink in a pub last night.

fire at = not a very good choice of words. 

To be up to scratch: People who have attended school and studied for years are usually not up to scratch for the modern corporate world.



The big picture: This investment plan might seem ineffective at the moment, but if you look at the big picture it can earn you a wealth/lot of money when you retire.



Blue collar: There's no shame on being a blue collar worker since you make more/much more money .

you sentence suggested only self employed people earned more money.



By the book: We are told to be a good kid at school, but the corporate world doesn't function by the book.

"we are told to obey/abide by the rules , but the corporate world doesn't function by the book"

actually a more common expression/idiom is "play by the rules"

"we are told to obey the rules in school, but the corporate world doesn't play by the rules" 

There are still many of them on that link. Thanks for taking the time. Corrections and feedback are appreciated.

Your written English is very good. All sentences work but some need minor adjustments to use more natural native words.