There are some very strange words and expressions that people find in Chinese/English dictionaries, Alice. Many of them are either wrong, or virtually non-existent. If there's something in a Chinese dictionary or textbook that you can't find in an English-English dictionary, then it's probably not worth worrying about.

You can forget about 'tyro' for a start. This word is NEVER used.

Tyro - is not commonly used in English, I had to look it up even ;)

Trade = A trade is something like mechanics, carpenter, chef etc. 

Art - (i think) means = Learning music, art (visual art), langauge

It would be better to say you are 'an apprentice ______(something)'. In Australia, apprenticeships go for 3-4 years usually, so if i said "hey man, what do you do for a living?" he/ she may answer "Oh, i'm a second year apprentice chef". Once you have finished your apprenticeship you become, 'a qualified tradesperson' or in Australia 'a tradie'. 

Could I replace learner with beginner, novice or tyro ? = It is grammatically correct, and people will understand what you mean, but - being an apprentice = means you are learning, you are a beginner. So if wouldn't be necessary to use these words. 

Hope this helps

OMG...Thank you so much!^ ^Su.ki, you are so nice! And your suggestions are really helpful! I think it is horrible that we often meet words seldom being used or even not existing.....and we don't know that. I often use dictionaries like Urban Dictionary and Langman Dictionary, so when I found tyro in Urban but not in Langman, I was confused. Could you recommend me some authorized dictionaries?

By the way, different people from different countrys speak English with different vocabs. That's the thing which troubles me a lot. I tended to speak American English when I was in university, because it was popular at that time. And after graduated, I love British English more, for its beautiful accent and charming syntactic structure. However, I still need to learn American English, coz both of AmE and BrE are popular now. How do you deal with the problems you meet when you communicate with other English-speaking countires' people?

I ask for your consideration, kind-hearted Su.Ki;)~~I wish you will not feel bothered, coz I really talk a lot. And I am not sure whether this kind of expression is proper or not, if you feel weird or something else alike, pls tell me.

Thank you! Su.Ki!XD  I agree with you, coz I can't find it in Longman Dictionary. And I don't know in which context it would be used. I am a little curious about it