First, welcome to the forum.
Second, 15 celcius (59F) is awful low for US-04, which is likely causing the slower fermentation. I recognize the temps have been raised but you also have to allow time for the yeast to replicate. Please understand that the first week those yeast were really sluggish.
Again, welcome to the forum and don't worry about the language barrier. We'll figure it out! And thank you for the kind words. Please feel free to ask questions and share any knowledge that you have!