I appreciate your [STRIKE]advices[/STRIKE] advice. Thank you very much.
I would like to ask one more question.
You say my non-relative clause incorrect. My non-relative clause is inappropriate because it is not a clause. It does not have a subject and a predicate. Is it?
Minoru is a happy man, who has a happy face, and he is Japanese. We practice Japanese, but I rarely read the meaning behind his happy face. For someone who [STRIKE]have[/STRIKE] has Minoru's character, I can hardly determine if his or her (you already said Minoru is a man so "his") gesture towards me is good or bad.
Is this better version?
Well, this paragraph is easier to read but it's much simpler and I don't think it conveys quite the same meaning. I have made a couple of corrections to it, but I also have some other points:
Sentence 1 = "...is a happy man who has a happy face and he is Japanese". That's a lot of words to say very little. You could simply say "Minoru is a Japanese man who always looks happy".
Sentence 2 = "We practice Japanese". Is Japanese not your native language? If it is, then "we speak Japanese". If not, then maybe "We practice our Japanese together" gives a better idea that it is a second language.
Sentence 2 = "I rarely read the meaning behind his happy face". Why do you think there is another emotion going on behind his happy face? At the very least, you need to say "I
can rarely read the meaning...." to show that it's something you are trying to do, but failing.
Sentence 3 = "For someone who has Minoru's character..." Who has Minoru's character? Are you still talking about Minoru, about someone else, or suggesting that you share his character?
Sentence 3 = "I can hardly determine..." We don't use determine very often like this. A more natural sentence would be "I can hardly tell..."
Sentence 3 = "his or her..." You already said that Minoru is a man. If you are still talking about Minoru's gesture, then use "his". If you are talking about "someone with Minoru's character" use the all-encompassing "their" instead of "his or her"
Sentence 3 = "gesture towards me..." What gesture are you talking about? You haven't mentioned a gesture, so the reader doesn't understand what it is that you're trying to work out.
Here is my suggested version:
Minoru is a Japanese man who always appears happy. We practice our Japanese together, but I can't always tell how he's feeling behind that happy face. With people like Minoru, it's difficult to tell the true feeling behind their words and gestures.
I'm not a grammar expert, so I haven't answered your "non-relative clause" question. I will leave that up to someone else!
Note: Remember to capitalise the word "I". Also, we don't pluralise "advice". Even though more than one person helped you, you still say "Thanks for your advice".