I want to improve my English, because I want to give classes to my students. They have visual impairment, so listening is crucial to them. It's going to be a big challenge for me.
because I want to teach English to my students.
We would say, "They are visually impaired" instead of they HAVE visual impairment.
They are visually impaired so teaching them English will be a big challenge for me, since I won't be able to use a lot of pictures and text.