How do i know wether it's sees fish or sees a fish? Like what part of the sentence is telling me that.
No, that would be plural "ryby". English has "fish" in both singular and plural, Czech does not have the same form.
Or, just see my comment above.
An exception is liking it as food. Then "I like fish." can be "Mám rád rybu." but plural "Mám rád ryby." is much more common (because there are many species).
Thank you. I am Ukrainian, therefore it is easier for me to comprehend Czech directly, not by means of English. In Ukrainian we can say багато риби (hodně ryby). As far as I understand, the Czech language doesn't allow this.
If it means many individual fish then not.
If it means you eat a lot of meat from a fish then it can be "hodně ryby". "I ate a lot of fish." "Snědl jsem hodně ryby." "ryb" would mean you ate multiple individual fish.