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

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

What month of the year has 28 days?

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 person was found dead on a big green land with no trees or buildings around. When the police arrived, they found a piece of rock lying next to him and the man was wearing clothes comprising of red, blue and yellow colours.

Can you tell who the person is and what was the cause of death?

Always in you, Sometimes on you;

If I surround you, I can kill you.

What am I?

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?

How many times can you subtract the number two from the number fifty?

How many sides does a circle have?

I am a white box having no key or lid.
Yet there is a golden treasure inside it.

What Am I?