I totally forgot about that.
我完全忘记了。

totally
完全的；全部地
completely;absolutely
This behaviour is totally unacceptable.
这种行为是完全不能 接受的。
I totally agree with you.
我完全赞同你。

A:Sally,don't forget that we have a neighborhood committee meeting tonight.
莎莉，别忘了我们今晚居委会要开会。
B:Oh!I totally forgot about that.
哦！我都完全忘了这回事。
A:Aren't you glad that I reminded you?
你难道不庆幸我提醒你吗？
B:Yes.Thanks a million,Tom.
是的。万分感谢，汤姆。
A:I think we are going to talk about buying new playground equipment tonight.
我想我们今晚要谈的是给运动场添置新器材的事情。
B:Yes,that's right.We need it badly.
是的，你说得对。我们非常需要新器材。
A:Indeed.So see you tonight.
确实如此。那么今晚见。
B:See you then.
到时候见。