I've thought a lot about this.

I've thought a lot about this the past few days. / Я много об этом думал последние несколько дней.

I'm just tired of thinking about it.

I'm just tired of thinking about it. Let's just relax and watch a movie. / Я уже устал об этом думать. Давай просто расслабимся и посомтрим кино.

You haven't even talked to me about it.

Why do you think I would be voting for the Turd Sandwich? You haven't even talked to me about it. / Почему ты думаешь, что я буду голосовать за Говносэндвич (Клинтон)? Ты со мной об этом даже не разговаривал. (из сериала South Park)

We've heard all about that.

This is difficult for me to talk about.

I've heard of that.

You seem to know a lot about this stuff.

You seem to know a lot about this stuff. Have you been on a date before? / Похоже, ты много об этом знаешь. Ты раньше был на свидании?

Have you heard about this?

Bill is going to marry his boyfriend Jim. Have you heard about this? / Билл собирается жениться на своем бойфренде Джиме. Вы слышали об этом?

That's what I'm talking about.