>>213528337
>Everyone but me in this thread is too intelligent that my stupidity stands out...
I think your English is pretty good, but I understand the awkward feeling of taking a long time to type or being uncertain about minor details that could potentially be big details. When I was a kid I would add "sorry for my bad english" almost all the time because I had no confidence in it yet, most likely because while I was able to write okay it took me quite a while to formulate myself which made me feel bad even if the written end result was passable. I feel the same with Japanese now, but I try to pretend like I know what I am doing so I feel more confident.
To me your written English appears very good.

>Google says there's the difference in nuance between ”don't understand him" and "can't understand him" but I'm not 100% sure...
In this specific scenario they mean almost the same thing so I wouldn't react if someone used one over the other in any scenario, but I feel like don't is more gentle than can't since it leaves more room for being able to understand.
>If not, would anyone like to dumb down the subtle difference between the two for me?
If you look at it from the angle of "I don't eat ice cream" and "I can't eat ice cream", the former means you don't for some reason (taste/diet/health concerns), the other means you are unable to (allergy,diabetes, also dieting).