Cuántos años tienes tú? - this means "how many years do you have" / "how old are you." You have to answer in this format: "Tengo (number) años." ("I have _____ years."
¿Tienes una familia grande o pequeña? - do you have a large or small family? Again you are using the "to have" verb "tener" so you need to use the yo/I form "tengo" and answer "Tengo una familia (grande or pequeña)."
¿Cómo es tu familia? - basically asking what is your family like? Maybe you want to say that you are all quiet, fun-loving, or something else? You should look up some Spanish adjectives that would fit, and would answer in this format: "Mi familia es (Spanish adjective)." Make sure you use the right form of the adjective that matches up with the singular and feminine "familia."
¿Tienes hermanos? Si tienes hermanos, ¿cómo se llaman?
Do you have siblings and if so, what are their names?
You are once again using the verb "tener" so you need to answer with the correct form of "tener" (the yo/I form) at the start of the sentence, and then, the correct form of "llamarse" to talk about the names of your siblings (would be singular or plural depending on how many siblings you have).
Examples:
"Si, tengo un hermano y una hermana. Se llaman June and Johnny."
"No, yo no tengo hermanos."
¿Cuántos años tiene tu mamá o tu papá?
How old is your mom or dad?
You use the same verb that is in the question, "tener" / to have and use the proper form "tiene" - the his/her/"formal you" form.
You could answer for example: "Mi mamá tiene (number) años."
"Mi mamá tiene (number) años y mi papá tiene (number) años."
