This is Michael. Here are some common mistakes I saw for the Warm Up videos.
When you are unsure about a word you can check here, dictionary.com . It is an American program so some words are different than the British spelling. It will usually have both words though (such as color and colour). Try it out.
Also, make sure you know the difference between ´´fun´´ and ´´funny.´´ It is not the same in English. Fun is when you enjoy something or it describes something you enjoy (such as, ´´I had fun last night.´´ or ´´It was a fun game.´´). Funny describes something that makes you laugh (for example, ´´I thought the movie was funny even though I did
not enjoy it.´´ or ´´I think he is a very funny person.´´).
There seemed to be some trouble with grammar and spelling. I have two recommendations. First, copy and paste everything that you wrote into a program that reads English. They usually have a button that, when pressed, corrects your spelling and some of your grammar mistakes. Read through each one, especially the grammar corrections, because they are not always correct. Microsoft Word, and even Gmail has this option. Second, when you are finished writing, read everything you have out loud. If something does not sound correct, it might not be. If you find a mistake, change it, and then start from the beginning or the paragraph again. If you do both options make sure you do the reading out loud second, because the corrections made by the program may not be what you want.