Hi, 'You'll just take..' doesn't quite make sense. You would need to say.. You'll just HAVE TO accept it and stay calm (something like 'solo tendrás que aceptarlo..' I think!) and yes, this has a similar meaning to 'All you can do is accept it and stay calm'

If someone corrected the first one to the second one, you probably should take less notice of that person's corrections.

Your statement, "You'll LL just take all on board and stay calm." I don't know what this says. What is LL? Your question, "I was wondering if will + just is enough to say the same thing" "You'll just" means "You will just," so you can say, "You will just..." in a sentence where "You'll just" is correct. However, "You will (or "you'll) just take all on board and stay calm," does not make sense. You will just take WHAT on board and stay calm? Your title question, "You'll just + verb , what does it mean ? Could it be replaced by' all you can + verb?" "You'll just [verb/action]" cannot always be replaced with "all you can [verb/action]. for example: "You'll just take all of them on board and stay [remain] calm," is a command. "You will just take all of them on board and remain calm," is the same sentence (without the contraction). "All you can take all of them on board and stay/remain calm," does not make any sense. "Just take them all on board and remain calm," is probably my favorite way to word this sentence.