我们从2000年开始谈恋爱----译成英文

你好，让我来答吧！
书面：we began our romantic relationship in 2000.
地道口语： we began dating each other since year 2000.

ps：那位自称是美籍中国人的家伙有很多语法错误，真假难辨啊～～～

We've been dating since the year 2000.

We had falled in love since 2 thousand year.

We've been in love since the year 2000.

We have been going out since 2000.

(I am American Chinese. This sounds more native compared to "fall in love", "date", etc.)

"你好，让我来答吧！
书面：we began our romantic relationship in 2000.
地道口语： we began dating each other since year 2000.

ps：那位自称是美籍中国人的家伙有很多语法错误，真假难辨啊～～～"

Are you kidding me? Who the Hell speak like this? If you want to use past tense, you should say "began... in 2000 " as "begin" is a verb for short moments. If you would rather go with " since the year 2000", then it would be better to use " have begun".
My English is perfectly f