Hi Hela,

1) How could I finish this sentence?
“What politicians say and what they do …are two different things (this is a very comon and natural expression here, but it isn't idiomatic) 

Is there an idiomatic expression for this special case ? It reminds me of an Italian proverb which says “Fra il dire et il fare, c’e il mare” i.e. there’s a huge gap / difference between what one says and what one does. Is there an equivalent in English ? Maybe, can't think of one right now

2) Would you please give me a sentence with the expression « sell-by date ». I don’t see what it means exactly.
More common, at least where I live, would be 'the best-by date'. On a milk carton, for example, this really means 'do not use this milk after this date', so I guess stores would normally remove unsold cartons from the shelves. 

We'd better throw out this milk, it's past its best-by date.

Also known as 'the expiry date'.

3) If ever somebody understands French, would you please tell me how can I translate this sentence ?

Puisse cet exercice éveiller votre curiosité à l'égard des verbes à particules !
May this exercise … awaken your curiosity with regard to the phrasal verbs! (however, this is not really idiomatic)

This thread has reminded me of an expression I haven't heard for a long time: "twixt cup and lip there's many a slip'.  I'm not sure what it means....does it apply here in #1?

Some places now print a 'best by date' or in the case of meat, 'use or freeze by date'.

Brewer has this explanation:

Ancaeos Helmsman of the ship Argo, after the death of Tiphys. He was told by a slave that he would never live to taste the wine of his vineyards. When a bottle made from his own grapes was set before him, he sent for the slave to laugh at his prognostications; but the slave made answer, "There's many a slip 'twixt the cup and the lip." At this instant a messenger came in, and told Ancæos that a wild boar was laying his vineyard waste, whereupon he set down his cup, went out against the boar, and was killed in the encounter.

MrP

Thank you all for your help.

Dear Mr Pedantic, thank you for your greetings. I'm glad to be back and work with you all again. I didn't do any translation exercises this summer, unfortunately, for I had so many problems to tackle. I had an awful time and haven't been to the beach once! Some of my worries (mes soucis ?) are not resolved yet, but I intend to forget about them a little by getting back to work.

I'm glad that I wouldn't have to use those complicated codes to highlight, underline, italicize... words! Thank you moderators.

All the best,

Hela