I think it really depends on what you're finding hard about it. Most of the time when I find a language hard it's because I don't understand something. Once I figure it out or someone explains it to me, everything falls into place. I don't know how you're using it, but I always find that DuoLingo is the best teacher I ever had. At the beginning of every lesson they have notes that explain the grammar, the how and the why and other useful tidbits of relevant information. And if you ever don't understand something, you can leave a comment on the exercise asking for help with something and other users can reply to you if someone hasn't asked already. I think with a community willing to help and explain things, languages get much easier. Right now, I'm struggling with a lot of Korean grammar mainly due to the fact I don't have anyone to ask about it and because google doesn't really include the characters in my search terms, it's not of much help.

Even moreso than DuoLingo, if grammar is where you're having issues with German, if you're willing to spend a little, I'd recommend Babbel. I use it for Norwegian and they have a good amount of exercises that are specifically for grammar especially on the tricky things. They also use culturally relevant words and sentences - things you'd actually see in an everyday basis in the countries that speak the language. 

Dear Beatriz

Any language is difficult to hard to learn, especially if you are a perfectionist. However, it can be done: our human brains are made for it! Children learn language easily because they aren't worried about making mistakes and just go for it. They don't get puzzled about grammar, they just imitate what they hear and pick up patterns. That's how you learned your native language. If you would learn your native language now, as an adult, you might find it just as difficult as learning German.

As an adult, if you start out learning a language you need to be patient and kind to yourself. Acknowledge that you won't be speaking like a native speaker straight away. You will only become truly proficient and fluent if you are immersed in a language, i.e. if you lived in a German speaking country for some time. Until then, be proud if you can communicate, even if it isn't perfect. Start trying to understand grammar bit by bit and have fun with it! Be curious.

I agree duolingo is a lovely app, especially as they are very encouraging and you feel like you are improving. I used to use duolingo with my school students for homework.

Having said that, I would be happy to tutor you and try to make you feel more optimistic about learning German :) Have a look at my profile and contact me if you think that I would be able to help you: https://www.italki.com/lisi.von.aster

Good luck!