有個do 字其實有咩分別ga?

大致上沒有分別,
加個 do 字, 只是加強了語氣。
等同下列句子 : --
我想去見識一o下..........
我好想去見識一o下........

Adding "do" before the verb "believe" is to emphasize that you really believe, and this "do" is an auxiliary verb and it should be changed to the singular form "does" if it follows a singular pronoun, like he, she, it.

do 在這兒有"真的"的意思

即 they "really" believe in something.

當然可以有其他解法。