I like to try to identify when one language influences another. Nowadays, our four-year-old consequently asks ‘Hur många år har du?’ in Swedish. Earlier in his life, he correctly used to use the verb ‘be’ here, but lately he selects ‘have’, like in Catalan.
There are other more ambiguous cases. I believe that phrases like ‘Det är sin bil’ as well as ‘Ingen får inte göra det’ (Nobody must not do that) are examples of when his Swedish is being adapted to Catalan grammar. But pronouns and negations are difficult to master, so it might well be that such errors occur also among children who grow up in Sweden.
A peculiarity is that he uses ‘(allt) för’ to mean ‘very’, as in ‘Det är för bra’ (That is too good). Is that because ‘too’ is a concept hard to grasp or is it yet another Catalanism? I assume that 'That is very good' can be expressed as ‘Això és força bé’ in the school yard. And ‘força’ sounds a bit like Swedish ‘för’, does it not?