From what I understand the concept of Trinity is 3 persons who are one and the same. Is this correct?
Yes. But your statement is incomplete. Trinity is 3 persons who are one and the same God NOT one and the same person.
So from this understanding, would you say God(Father) sent Jesus or would you say God(Father) is Jesus also?
Catholics claim God the Father sent Jesus. They do not say God the Father is Jesus, because Father, Son and the Holy Spirit are three distinct persons.
Is Jesus God or not? And is he All-Knowing like God?
Jesus is God and so he is omniscience (knows everything that there is to know).
I assume the distinction and the similarity between the three persons of the trinity is causing you confusion.
251 In order to articulate the dogma of the Trinity, the Church had to develop her own terminology with the help of certain notions of philosophical origin: 'substance', 'person/hypostasis', 'relation'.
252The Church uses
- the term 'substance' (rendered also at times by 'essence' or 'nature') to designate the divine being in its unity,
- the term 'person' or 'hypostasis' to designate the Father, Son and Holy Spirit in the real distinction among them, and
- the term 'relation' to designate the fact that their distinction lies in the relationship of each to the others.
253The Trinity is One. We do not confess three Gods, but one God in three persons, the 'consubstantial Trinity'
254/255 The divine persons are really distinct from one another and are relative to one another.