[求譯] 這段句子翻譯是否正確？
前文：
Since Chinese President Xi Jinping proposed the establishment of an Asian
Infrastructure Investment Bank (AIIB) during his Southeast Asia trip in
October 2013, China has dedicated significant political, economic, and
diplomatic effort to ensuring a successful launch of the financial
institution.
自從中國國家主席習近平在2013年10月進行東南亞訪問之旅時，提議設立亞洲基礎設施
投資銀行（AIIB）之後，為了確保能順利推動這個金融機構，中國便一直致力於重要的
政治、經濟和外交事務。
試譯：
These efforts culminated in the signing of a Memorandum of Understanding
on the establishment of AIIB by 21 Asian countries in October 2014.
這些努力在21個亞洲國家簽署AIIB諒解備忘錄後達到最高點（高潮？），
※請問culminated in這樣翻對嗎？.....(某事件)達到高潮
China has extended the deadline for countries to join as a founding
member to March 31, 2015: six more countries have since joined and more are
being lobbied, including Australia and South Korea.
中國更延長了各國加入AIIB作為創始成員國的期限至2015年3月底：自那時起，
AIIB已增加了6個國家（參與國現為27個），還在游說其他國家加入，
包含澳大利亞和南韓。
※請問上述翻譯是否有誤解原意？
six more countries have since joined...
since放的位置不知道怎麼翻譯，就直接翻成"自那時起"
想詢問版上大大這句話應該如何理解？
謝謝指教！！
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03/13 04:27, , 1F
03/13 04:27, 1F