what is the most difficult in learning english for me?

I think, the most difficult things are learning grammar and making sentences. This is because I was learned English at school, and at that time I was studying some grammar points, but it was a very chaotically, without any system. It's like a one day I was studying past present, and another day I was studying present perfect, but I absolutely don't know why we were studying those two points or how to use them. And now, my brain still does not have any system, and it is absolutely 一片空白 in my brain. So, actually, studying English is a little boring for me. But I have no choice. In the modern world, if you can't speak English, you will have so much trouble because of that. For example, if you are travelling in Europe, or any English speaking country, you will need to have a conversation with maintenance staff or with passersby (for the asking for directions). Of course, that is not all.
Thank you! I hope you can help me with this text =)