Hard time hearing/understanding old people, black English, how can I improve?

I grew up in foreign country and came to California in high school.Luckily, I can speak fluent English, but do have hard time understanding certain pe

I grew up in foreign country and came to California in high school.
Luckily, I can speak fluent English, but do have hard time understanding certain people.
For example, when I speak with white elderly person, (I have no problem understanding white adult) I can't hear/understand 10-30% of the times. It may be related to vocabulary/idioms old people use sometimes but I am sure I just don't understand accent sometimes.
When I listen to black English, I don't understand 60-90%. (I recently watched Last Chance U on Netflix, and I don't understand what these black college students were saying most of the times without subtitles). When I talked with security person who was black, I had no problem understanding. but, when that security person was talking with fellow black friend, I had no idea what they were saying.

So my question is, how can I hear/understand better old people and black English?
Are there any good resources?
I thought about watching TV shows/movies, but I couldn't find good examples (I have Netflix and amazon prime video).
Thanks for your help!

or:I grew up in foreign country and came to California in high school.Luckily, I can speak fluent English, but do have hard time understanding certain people.For example, when I speak with white elderly person, (I have no problem understanding white adult) I can't hear/understand 10-30% of the times. It may be related to vocabulary/idioms old people use sometimes but I am sure I just don't understand accent sometimes. When I listen to black English, I don't understand 60-90%. (I recently watched Last Chance U on Netflix, and I don't understand what these black college students were saying most of the times without subtitles). When I talked with security person who was black, I had no problem understanding. but, when that security person was talking with fellow black friend, I had no idea what they were saying.So my question is, how can I hear/understand better old people and black English?Are there any good resources?I thought about watching TV shows/movies, but I couldn't find good examples (I have Netflix and amazon prime video).Thanks for your help!

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