"I cook dinner."
Translation:Ik kook avondeten.
Basically, in Dutch the word "diner" refers to the event, not to the meal. Usually it implies something fancy, a special occasion. For example, "een kerstdiner" is a Christmas dinner.
If you are talking in English about "a dinner" or "the dinner", then the Dutch "diner" could work. It this sentence, it doesn't.
"Ik maak het avondeten" sounds more natural than "Ik kook avondeten", especially considering "het" HAS to be part of the sentence. E.g. Imagine a groupleader looking for volonteers to prepare the meals for the day; a groupmember stands up and says "ik MAAK wel HET avondeten"; it would sound out of place if he said "ik kook avondeten". Better sounding would be "ik maak wel het avondeten; ik kook Nassi-Goreng.