随便用英文怎么说
whatever
is fine, but sometimes it may sound a bit impatient and unfriendly.
here are some other expressions that you can try.
I'm down for anything. 我都可以
Up to you 你决定
I don't mind 我不介意
I've got not preference. 我都没差
It's your call 由你决定
You are the boss. 你说了算