Improve by communicating in English with people as much as you can. Also you could skype me and i could help you out and tell you how to improve.

It makes sense in everyway ... It's perfectly fine but generally people aren't so descriptive and would just usually say ... I have to work hard to keep myself from obtaining or receiving bad or poor marks

You could look online for English language vocabulary test and could do a simple test or reading a paragraph of english and see if there is any words you don't know or understand. Ways to improve look online for websites for English vocabulary (sorry for the slightly usless help. I'm not learning english at all) But if you tell me what level of english you are at .. i should be able to help you find some websites to help you ?

Symbolize means "to be a symbol" "to represent by a symbol" example for symbol would be (example) The Peace sign while stand for would be taking about what a symbol means or stands for example the Peace sign is a world known symbol for peace

Yes can be used for general agreement to a subject. While absolutey and definitely is a STRONG agreement to a subject ( mainly the terms of when talking to a person )

" but try and hang one of those suckers on the wall." The speaker is joking as 'the aztec stone tablets huge complicated' (which also means it's very heavy) So when they say 'try and hang one of the stone tablets on the wall' there are joking (due to the weight of the tablet)

"Or" is correct. Using "and" can confuse others as it's usually incorrect depending on the situation ~

it's wrong to pick on someone