To spot mistakes you have to speak the language very well. Although I think someone wrote 'kaupunginosa' somewhere.
Plurals are my bane, and any tense beyond the present and the imperfektiivi will leave me knowing the general idea of what is said but not the details - I could be doing worse after only a year. We'll see how the kesäkurssi thing works.
BUT these things go like that. In Spanish you have far more tenses and instead of cases you use prepositions always modifying the nominative, plus we have two genders and a lot of agreement between nouns, articles, numbers and adjectives. So it's quite confusing even for Finns who've spoken it for a decade or two.
One thing I have trouble with is pronouncing condensed words. Should I place a secondary stress on each new unit? Such as Harjoituskirja: /'harjɔitusˌkirja/?
It is Greek homework day anyway so my mind is on a different paradigm: even the numbers have gender, and you have to place articles everywhere -and declense them of course.