firstly の英語での意味
firstlyfirstly /ˈfɜːstli $ -ɜːr-/ adverb [sentence adverb] 
すべての翻訳を見る used to say that the fact or reason that you are going to mention is the first one and will be followed by othersこれから述べる事実や理由が最初のものであり、他のものが続くことを示すのに用いる OPP lastly: 
Firstly, I would like to thank everyone who has contributed to this success.Firstly、このたびの成功に貢献してくださったすべての方に感謝申し上げます。► see thesaurus at first
すべての翻訳を見る used to say that the fact or reason that you are going to mention is the first one and will be followed by othersこれから述べる事実や理由が最初のものであり、他のものが続くことを示すのに用いる OPP lastly: Firstly, I would like to thank everyone who has contributed to this success.Firstly、このたびの成功に貢献してくださったすべての方に感謝申し上げます。► see thesaurus at first