Bring Your Proof If You Are Truthful!

We find this phrase in quran. Let's examine it.

S 2:111 And they said: None will enter the Jannah but those who were Jewish or Nasara. Those are their desires. Say: Bring your proof if you are truthful.

S 21:24 Or have they taken gods instead of him? Say: Bring your proof. This is a remembrance for him who is with me and a remembrance for him who was before. But most of them do not know the truth so they are averse.

S 27:64 Or he who begins the creation then repeats it and he who provides you from the sky and the Earth? Is there a god with Allah? Say: Bring your proof if you are truthful.

A similar one is:

S 28:75 And we withdrew from every nation a witness and said: Bring your proof. So they knew that the truth is Lah’s and what they used to fabricate strayed from them.

If a man is truthful, he will be able to bring proof? Do the verses imply that people were lying? Did Allah's boss, who was supposedly truthful, bring proof?

Proofs?

Qur'an Contradiction: Did the Jews kill prophets who brought a sacrifice devoured by fire?

Is He a Messenger?

In Kuntum Sadiqin If You are Truthful