1.整个句子中并不含有什么宾语从句.
它是一个典型的主系表句型.
it是该句的形式主语.
is necessary是系表结构,即系动词is + 表语necessary.
而后面的(for them) to learn the language则是真正的主语.
2.in order to commuincate with these people and to learn from them
= in order to commuincate with these people and (in order) to learn from them
这是俩个用and并列的不定式短语,做句子的目的状语.
3.翻译：
为了和这些人们交流/沟通并向其学习,（对）他们（来说,）学习这门语言是有必要的.