Becoming bilingual doesn’t just mean you learn a few foreign words.
It’s means you learn to model the world with different words and labels.
That includes all the vocabulary for each object, but it also includes learning all the verbs – the actions. Retourner la feuille = turn over the paper, for example in English.
The world might be modelled in a different way in each language, especially when it comes to certain concepts. This is when comparing languages becomes interesting and merits much more than a small blog post.
It’s also obvious that modelling the world with new labels is going to take time.