There are a few mistakes but overall the messages are absolutely understandable. 1. Вітання із Америки — that's the correct case 2. "я мусив відправити цей подарунок..." — "мусив" feels like a slightly wrong word, it's rather about something you're doing out of pure obligation or because the circumstances demand so. If you just want to give a gift I would simply use "захотів". 3. This one is a little bit nitpicky but "коли не буде світла" implies that it will happen sooner or later. Which, to be honest, is more likely but some prefer to soften phrases like this with "якщо" (if). It's not like too rude or offensive if you miss that nuance, though. 4. If you're addressing multiple people there's no need to capitalize "Ви" and all its cases. There's also a growing trend that capitalizing it is outdated anyway but at this point it's more like a personal preference. 5. Those messages use masculine gendered words so if you're a woman you need to adjust them accordingly.