As a starting point, use combien de when you've got the thing you're "counting" straight afterwards, for example: combien de pommes = how many apples.
Use combien on its own essentially when you don't have the thing you're "counting" directly afterwards. For example, when the word is right at the end of the sentence, which often happens when you're asking a question:
C'est combien? = How much is it? Il y en a combien? = How many are there?, How much is there?
Then how to form a question with "combien" and "est-ce que"?
Can I ask "Combien est-ce que c'est?"
" Combien de langues parlez-vous?" is that right?
Making a question is troubling me.
Meric !