In English we rarely omit words, even if its obvious what we're referring to. But I've noticed Chinese speakers sometimes do omit them and sometimes don't. Should the words in brackets be omitted or added? E.g.
- "你认为中文难吗？" "因为（它的）口语比我所有学过的语言难多了，所以（我觉得）（它) 难"
- "你想跟我一起去吗" "不想（去)"
- "你为什么不想去呢？" "因为（我）感觉有点不舒服了"
- "你感觉开心吗" "不感觉（开心）"
Also, in the 2nd example, I am wondering whether it should be 很难 instead of just 难?
As for answering questions, would I be right in saying that I should only ever answer using 是/是的 if the question uses 是 as well? E.g. 他是工程师吗？ 是/是的