Why isn't "She is eating the apple" "Sie ist isst den Apfel"
Isn't it logical for it to be "Sie ist isst Apfel"? Why is it "Sie isst Afel" instead? Where did the "is" go?
German has no distinction between "She is eating" and "She eats". I think by using "Sie ist isst den Apfel" you are meaning that she is actually the verb eat.
Try not to use one language with the rules of another. You have to think differently in a new language. Languages are not all the same just with different words. It is like driving a totally different vehicle instead of the same one with a different paint-job.