For me, both sentences sound a little weird. For the English part first"I have three members of the family" I think u mean "there are three members in my family" because "I" cannot have "members" ,it is weird. For the Chinese"我有三口人","我"is the subject,"有"is the verb,我有“三口人”is really strange for the same reason. In general,we say我家有三个人, and“口”is not a formal quantifier for person,if you want to say "three people/persons", you'd better say 三个人 because "口" is used as an old idiom and knowing but not using that would be a wise choice

say it to me is enough, don't tell it to another one anymore. 这个情况表示A觉得这件事情不方便公开说，B跟她吐吐槽就够了不要再说出去了 吐槽的意思是发牢骚，倒苦水，类似英文中gossip

我该用英文回答还是中文呢？ May I answer you question in Chinese or in English?

I'm not sure if whether should answer your question in English because it seems that you gave yourself a Japanese name, am I right? Anyway here is my explanation: "上升" and "下降" mean "goes up" or "goes down". These two words, I think, describe abstract things to indicate a trend. For example, "这条曲线在这里上升"="this curve goes up here" "增加" and "减少" mean "increase" or "decrease".These two words, in most circumstances,describe a change in number such as "我的工资增加了" =“my salary increases this year”. Actually for me, a native chinese guy, can not tell the difference between them accurately because Chinese is not a language so accurate as English, which means, a single chinese word may have different meanings in different situations and most similar words are interchangeable if slight bias in meaning is acceptable. It is really a tough question and I think you should not remember much rules but just read more and get used to some common use.Here are more examples: 中国的人口正在增加: the population of China is increasing. 海平面在过去的几年里一直在上升：the sea level has been rising in the past few years 股票价格一直在上升：the stock price is increasing; yeah, a tough one because it contradicts with my explanation above. So, let off the rules and just feel the language~ actually in chinese we always use"上涨"to describe increase in price. I think those is enough~

This is merely a test.

I just want to finish the registeration quickly.

I'm sorry to say that the meaning of the original text is a little weird. It seems that this paragraph is picked out of a fairy tale because the words"愿望炮弹", “愿望天堂” as well as“流星爷爷” are not commonly used in daily life, but in some stories parents will tell to their little child.For example, the word"流星爷爷", for me,a native Chinese guy, is kind of like "圣诞老人", which in English is "Santa Claus" ,rather than "Christmas Grandpa". Let me try to improve your translation to some extent: A countless unending stream of desires came into the heaven of desires from all around. However, these things do not matter for granddad Liuxing any more , because today he is going to retire. “Everyone, keep moving to be a better desire messenger” he said loudly to his colleagues. I'm a little confused about the word "desire".For me, desire is more like"欲望"rather than “愿望”. I think "wish" will be a better alternative, but I'm not sure. Sorry for that