TOO DIFFICULT, TOO MANY QUESTIONS, TOO MUCH TIME

Demasiado + adjective/adverb = TOO + adjective/adverb:

The fur coat is too expensive.

Question number four is too difficult.

These shoes are too big.

She speaks too quickly.

Demasiado "a secas" = TOO MUCH:

Don Quijote read too much.

I love her too much. (A strange thing to say, but it's possible)

Demasiado + uncountable noun = TOO MUCH + u. noun

He eats too much fruit / cereal.
She drinks too much milk.

There was too much traffic.

He gave us too much homework.

Some politicians earn too much money.

Demasiado + countable noun = TOO MANY + c. noun
She invited too many people.
Do you think there are too many children in this class?
Don't eat too many sweets!

An exception: He gave away too many clothes, and now he's got none. "Clothes" is actually not countable, but it is a special word, because it is both uncountable and plural (something rather unusual). TOO MUCH is never used with plurals, so we say too many clothes.

Common mistakes:

There was too much people >>> There were too many people. ("People" is countable AND plural)

It was too much hot / small, etc. >>> It was too hot / small, etc.  (¡Ni TOO MUCH ni TOO MANY: no acompaña a ningún sustantivo!)