OK, I just learned my ninth for language, Greek, over the past year. I didn't even mean to learn it, I was afraid of the dentist and I had to get through many appointments. The dentist is Greek. Say no more. I am now a member of the Greek Blind Union, and since there are hardly any videos on visual impairment or disability in Greek on YouTube, I've been making them myself. A good way to use my Greek.
I would love to learn Arabic, if I could get my hands on some braille. Or on a very very good audio course. A few years ago, I had an Arabic braille book, but absolutely no English to go with it and I couldn't figure it out. I was teaching two Blind girls, one from the rock and one from Algeria, I was teaching them English, and they weren't very far along with their English, so we struggled with not being able to understand each other, and because I cannot actually read Arabic print, not even large print, I couldn't use online resources.
I speak German, I learned it in high school along with French and Spanish. I grew up in Florida, so had access to lots of Spanish speakers, Spanish TV, etc. My mother is friends, but friends is actually not my favorite language. It still is not one of my best. With German, I loved it, thankfully I had a German speaking neighbor.
I lived in Italy for three years, that's where my Italian really came along since I was planning on attending the interpreters university interest today and I needed a high school diploma in Italy. I spent One year at an Italian high school and I only had Italian friends.
I lived for many years in central Vietnam, so that's how I learned Vietnamese. I couldn't read it though, until only a few years ago when I could access large print on my iPad, iPhone whatever. There also is a YouTube channel with audiobooks in Vietnamese and the audio library for the blind is free and online in Vietnam.
The key is to keep practicing, when you're in the shower, having dinner, use the language as much as he can. As much as you can. There is so much material available on YouTube in terms of television shows, films, news, start out with kids tv if you need to. That's what I did with Greek. Also, look for interesting apps in the language does he want, I have a Greek crossword puzzle app and in the beginning, I also had a Greek fairytale app that used to read the books aloud. If you have a special interest in cooking, gardening, whatever, look for blogs and things in the language you want. You might not be able to understand everything, but little by little you will get better. It takes a lot of work to get good at something, but it's definitely worth it