① 交通 means just 'traffic' and 渋滞 means traffic jam. e.g. 交通の便が良い: be easy to access 交通量が多い道路: heavy traffic route 渋滞のせいで遅れる: be late because of a traffic jam 渋滞につかまる: be caught by a traffic jam ② For example, 'one of the best～'　can be traslated to '～中でも最高級のxxx（noun）' . e.g. This is one of the best sushi I've ever eaten. 今まで食べた中でも最高級の寿司だ。 The reason I write 'for example' is that we can translate this phrase into different Japanese phrases according to the context. FYI ’This is the best sushi I've ever eaten.’　can be translated to '今まで食べた寿司の中で一番美味しい。' / '今まで食べた中で最高の寿司だ。'. ’中で一番’　/　’中で最高’ (without 'も’） implys ' the best' as only one, highliting the only one. '中でも’ (with ’も’） implys the comparison with the best group (the best group of sushi I have ever eaten). (I am sorry for my poor explanation.) ③ ’拝啓’　can　be used in extreme polite/honorary situations. This is just for your information. When you use ’拝啓’ at the beginning of the letter, you need to use ’敬具’ at the end of the letter. I hope my answer is helpful for you. If you have any questions about my answer, please feel free to comment on it.

1. 渋滞 traffic jam/congestion 交通 traffic 2. One of the best ~ ~(の中)で一番の/最高の一つ This is one of the best sushi I've ever eaten. これは私がこれまでに食べたすし(の中)で一番の一つです。 3. 拝啓 can be used in companies' official letters/notices/emails. But I would not use it in regular business emails. I do not know if it can be used in the Japanese immigration, which is a little tricky situation for me. Hope this helps.