... at a sports field (not: the) - jesli piszesz o nim po raz pierwszy
... I had / was taught by a famous instructor, but I don't remember his name
... demonstrated TO me... how to use the KITE (not kate ;-)
... we also watched/ observed him... (look for - szukac)
... all that we talked ABOUT
... I thought that it was easy
... the weather was nice / sunny/ it was a sunny day