hello i am learning here in duolingo german language it is not quite difficult but i think i cannot learn the all german language here does anybody knows if there you can learn any language perfectly because i cannot understand the grammar very good . i hope you understood me because i don't know the whole english language
You need to go slowly. Listen to the way the speaker says the words. You have to know the direct article before you can get the cases right. Make sure you read the explanations/grammar rules as you go along German is a very complicated language. Why are you trying to learn it. Go back and start from the very beginning to review. If you start making mistakes, you are setting yourself up for failure.
Duolingo can't hurt, but you will want other sources and practice. Don't worry about being perfect. Even native speakers make mistakes and you know that already from your own language. Viel Spaß beim Deutschlernen.
I have found two methods that are invaluable, in learning any language. Number one is immersion. But, since I live in Florida, that is difficult. So, I joined the local German-American club. Number two, and I consider this essential if you want to be fluent, and don't have access to immersion is formal education. I find Duolingo to be an invaluable tool to keep sharp, and pick up new words and phrases. It's the best free app, IMHO!