Are there any tools to automatically clean the RAM? Without cleaning one by one.

I'm using Samsung S6 Edge. I feel a little boring about the phone now.

1) How to install a 3D Theme? Will it make my phone slow? I have 2G RAM
2) Why is my phone getting hot while using facebook? Something wrong with the APP ?
3) My battery die faster than last month, any reasons for it?

Thanks for help in advance.