I think I would preserve the seasons but I would make it so there was 12 hours of sunshine and 12 hours of night every day.

I like that - it brought to mind a world with a hard and fast delineation between night and day - a 15 minute transition between the two.

I would change all the people so they could understand every language ever existed in earth.

I like the idea of understanding languages. I'd add speaking, writing and reading other languages as well.