"In my expert world I managed to beat the brain of Toulon as the first boss and outside the spiders by teleporting me to the spawn thanks to the mirror and destroying the last Heart thanks to a bomb once the brain conquered I recovered a treasure bag that told me that I had to open by double clicking on it but it does not work even if I have only 7 items in the inventory do I have to wait to have beaten the wall of flesh where is this a sorry bug for the inconvenience"
Hi, Kilian, you should be able to just double-tap (with a finger or stylus) on the bag in your inventory to open it, just as you would for a fishing crate, Halloween goodie bag or Christmas present.
I just verified that it works, and the English tooltip does say to double-tap it. Perhaps the French translation didn't get updated properly.
edit: Yes, we see there are problems with the translations, as well as additional problems when switching languages in-game (there are a mixture of languages when we do that). But double-tapping on the treasure bag should open it.