Shall I read the Catechism [of the Roman Catholic church], or the bible, but from which denomination? I believe in God, but which truth shall I believe in?
You ask: “Which truth shall I believe in?” First of all I would say: in the truth that convinces you, i.e. that makes sense to you, or that gives you a satisfying answer to your deepest desires and yearnings. What is it you yearn for ultimately?
Throughout history there have been various religions and founders of religions who claim to have the answer to their deepest questions and yearnings. The most important ones of these are Buddha, Jesus Christ and Mohammed.
In the following I will only engage in the truth claim Jesus still makes through his church today.
For us Christians this truth is the person of the crucified and resurrected Jesus of Nazareth. We know and experience in our faith the power of the Holy Spirit.
The truth claim of Jesus has been represented by the Christian church throughout the centuries. What, according to the message of the church, is this claim Jesus makes?
In order to discover this you should indeed first of all consult a Catechism of the Catholic Church and, if possible, to discuss these questions with a convinced Roman Catholic Christian. (See http://www.vatican.va/archive/ENG0015/_INDEX.HTM)
I will summarise the teachings of Jesus as proclaimed by the Roman Catholic Church from two aspects:
1. Jesus proclaims that God is love, that in him this loving God has finally and irrevocably turned towards humanity and in him all people are called and empowered to lead a life of self-giving love.
2. Jesus proclaims that people find their fulfilment and that they honour God, their creator and father, if they follow his call and allow themselves to be give the power to lead a life in self-giving love.