i don't understand the plural, nominativus, genetivus can someone explain it to me?
If its something like this, hiw do i tell if its singular or plural? Because you say Fish for a single fish, and Fish for multiple as well...
In this particular case, you don't -- both answers should be accepted. Otherwise: by context. (Two fish is probably plural ^^)
fisk is the singular and fiskar is the plural.
However, we often use fisk as a mass noun even if we are speaking of multiple fish. Especially when we talk about fish as food.
Isnt the plural of 'fish' in English 'fishes'? That should make it more clear when they want us to translate into the plural or singular in this case.
"fish" is actually usually the better option, although neither is incorrect.