Really and Simply

Hi all.

Please someone tells me about the difference between really and simply.

In the meantime, I know when some one tells a person about something interesing, he should answer really? and he can't say simply?

But if I want to say these sentences which should I use? Really or simply?

Here are the examples:

1.You really are beautiful/You simply are beautiful

2.You really made me happy/You simply made me happy

3. etc..

And please tell me where should I put really/simply in a sentence.

Look at these:

1. You really are happy 2. You are really happy.

Thank you.

JM.