Someone tricked me to sign a document without paying attention to content. The person also made 2 persons to sign the documents as witnesses. I want to withdraw the document, is it enough that the witnesses (or one of them) declares that he did not see the parties sign the documents in front of his eyes and consequently the witness is not valid?
With very few exceptions, documents do not need to be witnessed to be valid even where there is a space for a witness to sign.
When you knowingly signed it you were making a legal declaration that you had read it, that you understood it and that you agreed to be bound by it. If you didn’t “pay attention to the content” then more fool you.
As to being “tricked”, you would need to elaborate on this (in another question) it for this to have any effect it would need to ride to the level of misrepresentation or fraud - like substituting a different document for the one you had agreed to sign. You would also need evidence of the “trick”.
To get out of the contract, you would have to convince a judge that you didn't sign it (more precisely, that based on the facts it's more likely that you didn't sign the contract than that you did sign it). That would be difficult to achieve because you did sign it. The opposing lawyer could just ask you point blank: Did you sign this contract? And lying would be a crime.
Witnesses are not needed to show that you signed the contract. If a witness said "I didn't really watch who signed the contract, so I don't know if it was user34663 or someone else", they wouldn't count as witness, but the contract would still stand. If the witness said "I watched closely who signed the contract, and I'm 100% sure that it wasn't user34663", now that could convince a judge. Except the witness wouldn't say that because you did sign, so they would be lying.