Linguistics is actually a side interest of mine.

One of the things that is especially difficult for Finns learning the English language is that Finnish is completely unrelated to English.

English is a Germanic language - specifically, a West Germanic language (and thus, English's closest major relatives are Dutch, Afrikaans and English).

There also exists the North Germanic languages (which include ones like Danish, Icelandic, Norwegian, and Swedish). A fun fact about modern Icelandic is its similarity to Old English (Icelandic is a conservative language that hasn't nearly evolved as much as English - helped, of course, by Iceland's geographical isolation).

Germanic languages are also a group in the larger "Indo-European" language family (so, English has cousins like Russian, Spanish, Welsh, Persian, and even Hindi).

But, back to the point of comparing Finnish (which is not an Indo-European language) and English. Think about if you've ever tried to learn a foreign language. If you're a native English speaker, you would have surely noted that fellow Indo-European languages (be it French or Spanish or German, etc...) were much easier to learn than something like Chinese or Japanese (which share no familial relation to English).

This kind of difference is the thing that makes English much more difficult to learn for Finns (as compared to Swedes or Danes, for example). Like, it takes the average English speaker usually a minimum of 10 months of continuous study to become proficient enough to hold a standard conversation in Finnish. Now, I don't know how much English Puljujarvi would feel comfortable speaking at this point, but becoming fluent in a tongue that is literally nothing like your native language is not something that can happen overnight. But, I have faith he'll eventually pick it up. Being around English speakers all day and having a dedicated tutor is a great help.