You need to arrange three 7 and mathematical symbols to form number 1?

Can you decipher these quotes by Albert Einstein?
Blf xzm mvevi hloev z kilyovn lm gsv ovevo lm dsrxs rg dzh xivzgvw.

It's pretty hard to give up.
If you remove a part of it, you will be left with a bit.
Even if you remove another part, the bit still remains.
Remove one more and it still remains.

What is it?

I sleep during the day and fly at night, but I have no feathers to aid my flight. What am I?

A boy and a girl are sitting on the porch.
"I'm a boy," says the child with black hair.
"I'm a girl," says the child with red hair.
If at least one of them is lying, who is which?

I can write cow in 13 letters.

Can You?

I add 5 to 9 and get 2. The answer is correct, so what am I?

Look at me. I can bring a smile to your face, A tear to your eye, Or even a thought to your mind. But, I can't be seen. What am I?

If 5 cats catch 5 mice in 5 minutes, how long will it take one cat to catch a mouse?

Can you decipher the two rows to find the hidden word?