to tell lies or to tell a lie
I'm really confused when I should use to tell a lie and when I should use to tell lies
I never tell lies to my parents or I never tell a lie to my parents
there are a lot of cases like this
For ex: to read a story or to read stories
to take a risk or to take risks

Question

to tell lies or to tell a lie
I'm really confused when I should use to tell a lie and when I should use to tell lies
I never tell lies to my parents or I never tell a lie to my parents
there are  a lot of cases like this
 For ex: to read a story or to read stories
to take a risk or to take risks

Answer

Hey, Davood!

"I never tell lies to my parents" is correct. Because you are talking about telling lies, about the action, to lie. And you never do that.

About the other examples, "To read a story" indicate that you are talking about read one story. Whereas "To read stories" means you are talking about read different stories in different situations, for example:
Let me read a story for you.
or
I always read stories for my son.

I hope this helps!

Answer

One is singular. The other is plural. Both are good depending on the situation. If you are using 'never', I would use use never tell lies.

Answer

One is singular, the other is plural.  Both are correct.

لا تفوّت فرصة تعلّم لغة جديدة وأنت مرتاح في منزلك. تصفّح مجموعتنا المختارة من مدرّسي اللغات ذوي الخبرة وسجّل في درسك الأول الآن!