(it's) nothing important
Rien de rien - nothing at all
"Mais il n'y a pas de mousse" means "but there is no moss / foam / mousse" in English.
in a shake, in no time
It means, "it's nothing" or you're welcome.
Nothing at all, diddly squat.
"c'est rien de spécial" means in French "that's nothing special"
"Nothing new!" is an English equivalent of the French phrase Rien de nouveau! The prepositional phrase also translates as "No news!" in English. The pronunciation will be "ryad noo-vo" in northerly French and "ryeng duh noo-vo" in southerly French.
rien de neuf
You can say, "de rien," "pas de problème," or "il n'y a pas de quoi,".
"Mon coeur" means my heart. "Rein" means "kidney" (probably a mispelling of "Rien" meaning "nothing"). So "mon coeur et rien de plus" would read "my heart and nothing more" in English.
Rien de spécial means "nothing special."
non merci, c'est gentil de ta part, mais je ... means: no thanks, that's very kind of you, but I ...