在一起很久英语

We will be together for a long long time.如果是给外国人解释：我们：we要在：will be，future tense because it means we must／we should，it's not just for now一起：together好久好久：literally：goodly long，so it can also be：a good while，but its meaning is closer to very very long，and long long time is a more literal translation that makes sense

We're gonna be together for a long time.

We will stay together for a long time.

we will stay together for a long time

We've been together for a long time。

We are together for a long time