The more of this there is, the less you see. What is it?

O_er_t_o_

Complete the missing letters of the given word.

What has six faces, but does not wear makeup, has twenty-one eyes, but cannot see?

Fate has decided that you will only be pleased to meet me when you need me

Maybe that is why, when I am working, I start working

However annoying I may be to the regulars, the little ones are always inspired

I will always be waiting if you try to reach me

How many of you can guess my name, let me see

I go up and I go down.
I go up towards the beautiful sky and down toward the green ground.
I am present tense.
I am past tense too
Children love me.

Who Am I?

Count the number of times the letter "F" appears in the following paragraph:

FAY FRIED FIFTY POUNDS OF
SALTED FISH AND THREE POUNDS
OF DRY FENNEL FOR DINNER FOR
FORTY MEMBERS OF HER FATHER'S FAMILY.

A man and a dog were going down the street. The man rode, yet walked. What was the dog’s name?

I am white when I am dirty, and black when I am clean. What am I?

What is more useful when it is broken?

If I remove one from eleven it becomes Ten and if I remove one from nine also becomes Ten. How?