In Present simple^x, Speak english^x

I have a question. Firstly, I wanna tell you, that I´m from Czech Republic and I can´t speak English well, but I´m trying to improve it.So, my question: This is negative form of present simple: You are not... I can make it shorter: You aren´t... But can I do this: You´re not... I am not sure, I...

Of course I don't mind your asking I don't know what your first language is, but in my country, Spanish speakers find it difficult too to understand that the "s" is necessary to form the simple present of a verb for the 3rd. person singular. The reason is that we associate the addition of an "s"...