Why those names that listed by Stephen are undesired? can't understand.

I think the most effective way is to talk with Chinese as much as possible. We can exchange languages if you like. I am in Australia.

Come on! I don't think they belong to post-90s language. Actually, they are wildly used internet words. if you go to some Chinese forums, like Tianya(天涯) or Mop(猫扑), you will see them everywhere. "槑" is the same as "呆", which means "dull". "啥米" or "虾米" means "what". "雷到" often used to express a feeling of shock. If you are shocked or amused by something, you can say that thing is "太雷人了". There are some other popular internet words, like "囧" , "华丽丽" and so on. I think it'd be great if you could master them so that you could better communicate with Chinese young people and also it'd be much easier for you to read some websites. lol. If you want to learn, I can help you. Cheers.

I speak wenzhou dialect, which is considered the most difficult dialect in China. I don't think imitating an accent is being racist. people often do that for fun actually. I like imitate Tianjin accent. I used to work there for 3 years. Listening crosstalk(相声) in Tianjin accent is really amusing .

In my opinion, A,B,C,D 4 grades are enough for the score from 60(or 50) to 100. So we dont need E. F means Failed.

i think if you want a tattoo on your back, it's better off using a short phrase. So my suggestion is "柳暗花明", just four characters, which comes from an old poetry. The original sentence is "山穷水覆疑无路, 柳暗花明又一村", which means sometimes it seems that you are in a dead end, but if you keep walking you will see a brand new scenery. i think it well fit your situation. Hope it helps. take care.