は / が
I still don't funny understand when to use one or the other. The way it seems to me is, if I came across some animal with a friend and we had this conversation:
Me: これは何ですか (this here, what is it?)
Friend: 猫です (It is a cat)
Then I could say:
which means, I think it's a dog / It is a dog to me. But when I say
that means, I am a dog.
Would this be correct? The Duo course doesn't really explain what the difference is.
They're really completely different particles. Particle は indicates the topic of the sentence. In English, we only indicate topics on occasion, and when we do it often sounds very... odd. "As for me, I love cheesecake," or "When it comes to war, I hate firearms" are two examples. In Japanese, indicating the topic is a lot more common, though it's still optional.
Particle が indicates the subject of the sentence. Unlike in English, subjects are often implied by context in Japanese. In other words, you can omit the subject completely.
So what do you do when the same thing is both topic and subject? Well, if it's obvious by context, you can still omit it. But if you're going to indicate it, indicate it as the topic with は by default. If you want to provide emphasis for clarity, instead indicate it as the subject with が。
When will you use them both? Some sentences like 私は君が好きです (I like you) use both because, the way Japanese works, the topic and subject are different. Here 私 (meaning I) is the topic, not the subject. The subject is 君 (meaning you). You might translate the sentence as "as for me, you are liked." 私は日本語が下手です translates to "I am bad at Japanese" but you could phrase it as "When it comes to me, the Japanese Language is unskilled."
I watched a video in YT about it. Unfortunately it is in spanish. but I will try to explain you
は- we use it when the new information is after this particle. Example:
when you say 私は犬です, this means that being a dog is the new information
が-we use it when the new information is before this particle. Example:
when you say 私が犬です, this means that specifically you are the dog, in that phrase you are the new information, the focus is on you.
Another example, when your teacher asks to the students who was the one who was fighting during the class. And you want to take responsibility. you have to use ''が'' because you are focusing on you as the most important thing in the sentence. Unlike ''は'' that focuses that the importance of the sentence is after it.
English is not my native language, So maybe I got it wrong with something while I was writting, I hope it helps you a little, sorry :) I'm still learning.
It depends of the context
another example, when there is a group of dogs and between them there is one who bit that woman. And you know who bit the woman and you are gonna say who is. you have to use ''が'' just because it means you are focusing and who and not what happened. If the question is what happened with that dog (you know who dog is) you have to use ''は'' because the dog is not the importance, the importance is what that dog has done. Everything depends of the situation and the focus of the sentence. the context is really important in japanese.