So I can believe in whatever I want? No and yes, but it does not matter, let me explain what is really meant with that sentence.
Some religions propagate the claim that if you believe in a certain thing, you will be saved, go to heaven or whatever, but there is no logic behind it.
The mere fact that you believe in a certain thing does not change anything in reality and therefore it does not matter or make sense to do so. I'm talking here about the mere fact that you believe in something that does not matter. What matters is what you do, so you can have any belief in your mind, but what matters is your actions, not your belief, since only the actions you do can be cause for something. Your belief system can influence your actions, but there are also many people that have a certain belief, but their actions contradict their belief.
Another problem is, that acting purely on a belief is irrational, since anyone can believe in anything, there are no reasons or proofs needed. So your belief should be based on facts, not on imaginations. Once you have facts you can have faith, by faith meaning having trust in it. So a true belief should be based on something else than just randomly making things up and believing in it. But even all that does not matter when you do not act upon it, since only your actions cause real change in the world and can be cause for things that happen. Of course the mere existence of a belief system in ones mind can and will influence ones behavior already, but it is not as powerful of conscious action.
Our world would be very badly designed if it were all about randomly chosing the right belief system, which in itself does not change anything, it would all be like gambling, that would be a hell of a world to live in. You cannot go totally without belief in life, since you always have to asume something and believe in it, but if you have to do so, try to do it based on reason and logic. The logic regarding this is, that I can see actions causing change in the world and not belief that is hold in ones mind without doing anything.
An Example: If a person commits a crime against someone in this world and comes in front of a judge and says to his defense "But I believed I was doing good to that person" this will not work, since what counts is what he actually did, not what he believed to be doing. What may happen is that this person will be declared insane (rightfully so) and will receive different punishment for his crimes.
This is why I believe in actions and not in beliefs