This would really pull the reader into the environment.
Would it, though? I'm unconvinced - if anything I can see it having the opposite effect. Having chunks of dialog that the reader (presumably) wouldn't be able to understand is more likely to be exclusionary IMO. It's one thing to do this as a mechanism when you're in a POV that isn't intended to understand a given statement and you're using the narrative device of that POV's not understanding to illustrate a divide, but if I understand you properly you're intending that the reader be able to understand what is said and that this is going to be a relatively common thing.
This can work in visual media like T.V. and movies because they can make use of subtitles, so the viewer doesn't experience any lag in understanding what's being said. Doing that in text doesn't work because the reader has to read the foreign text then the translation; if it starts happening frequently, most readers will just skip over the foreign text and go straight to the translation. Either way you're chipping slightly at the immersion.
Marium turned to his mother and spoke rapidly 'Madre! L'anatra di gomma fiammeggiante parla di senso! Forse dovremmo ascoltarlo.'(The flaming rubber duck talks sense! Maybe we should listen to him)
Marium turned to his mother and spoke in rapid Italian 'Mother! The flaming rubber duck talks sense! Maybe we should listen to him'
The second quote effectively communicates to you that the character is speaking to their mother in Italian but they don't need to understand Italian to be able to read the text unimpeded. And anyone who can doesn't have to skip past redundant translations just to carry on with the story.
If you're just dropping the occasional word or short phrase you need to make sure that the context is good enough to provide a decent clue as to what is being said - and translations or glossaries are poor substitutes for where you've failed to do this. Here you can be making gains in terms of drawing the reader into the environment, e.g:
Marium turned to his mother and spoke in rapid Italian 'Madre! The flaming rubber duck talks sense! Maybe we should listen to him'
Even though we've told the reader the character is speaking in Italian, the use of Mardre! reinforces it and evokes the notion to the reader of the rest of the sentence "sounding" Italian - without them having to actually understand the language. "Madre" is close enough to "Mother" that with explicit mention of "mother" when he turns, most readers will (correctly) infer its meaning. Perhaps most importantly, if they don't manage to infer that meaning, they aren't going to struggle to understand what's going on in the story.