I am certainly more confident and can understand whatever I happen to read in English, which is of course of the utmost importance for my work in this company.

happen 的意思是"发生、碰巧"，表示偶然或意外的情况。 to 在这里是不定式符号，与 happen 构成固定搭配 happen to do sth，表示"碰巧做某事"。 happen to 这个短语表示"偶然发生、碰巧"，强调事情发生的偶然性。