1) First of all, B's response doesn't really make sense, since helmets do not affect your ability to climb the mountain. A would more likely say, "It's too dangerous to climb that mountain!" This way, B can suggest helmets as a safety measure. In this case, both "not a" and "no" work, but you'll probably never see someone use "in hell". Instead, they will use "in the world". So: "If you fall, not a helmet in the world will save you." or "If you fall, no helmet in the world will save you." The way you should use "in hell" is this: "If you fall, there's no way in hell a helmet will save you." 2) Use: "I don't want you to come to my house or my mom's." 3) The first two sentences are fine. The third is a little too forceful. It's more polite to say, "Could you please move?" Otherwise, you might come off as bossy. 4) Definitely use "you forgot". Also, use "when you go" not "when you goes". You can say: "It rained and and my room got all wet." "My room is soaking wet from the rain!" Essentially, use either "My room is [word for wetness] [because of/from] the rain." or "It rained and [now] my room [is/got] [word for wetness]."

1. If you fall from there, not a helmet or harness in hell will save you. If you fall from there, no helmet or harness in will save you. 2. I don't want you to come to my house, or my mom's either. 3. Please don't obstruct the fan/ventilator. I'm not getting any air here. 4. It rained and, because the window was open, my room got wet. I forgot to close my bedroom window and the rain came in.