If only you knew what a tough job it was!

If only you knew how much effort it took me!

Спасибо!
Давно хотела спросить, почему Вы не пишете перевод, а пишете ответ в комментах)
?

Это зависит от того, насколько я уверен в переводе.

This took me an immense effort to do it!!))

I worked on it as if my life depends on it.
I worked flat out from morning until night to achieve that.
That task was so monumental!

I worked on it by the sweat of my brow)
Естественно в начале предложения
If you only knew...

Thank you, everyone!

Пожалуйста)