For this time let we talk about tauhid, that means is believe to the God, and how to believe the God ?. So let we inform to you about that.

The first step, let we check, Does God exist?, Based on logic, maybe you can check around you, there are so many goods that made by human like phone chair,table, vehicle and etc not possible  if there are so many goods around you, Can that goods appear suddenly, do you believe that? I think It's ridiculous if you believe in that.
If things must be made by humans, why do you think this universe no one create it ? Example the earth include all in it, the moon, sun, Star, galaxy, and all in universe, why do you think there is no one create it. Base on my explanation before, definitely the God is Real,God exists. Okay and now.

The second step, if we know the God is Real and exist, we have to know Which God is really God? 
So let we make classification base on logicly.
1. God is one, why? If there are two more God, definitely we think who is the most powerfull God, or maybe the God Will fight with the rival. He he that is absurd.
2. Nothing is equal to God, Why? If someone claims to be God, there will be mutual claims that he is God. The African to be God, Asian to be God, europan to be God. So the creator  not same with creature. Okay do you understand, that is logic..!
3.God is not dependent like a creature, you know, let we give example the human need rice for eat,need water for drink,cooking,bathe, clean his rectum and etc, base on logic is God like that?
If you smart people i know your answer absolutly No, the God no needs all of it.
The creature need the God and the God no need you. We need God to pray and ask for everything and the God No need all of you.
based on the previous 3 classifications let's check all the religions in the world which are the same as this classification. After check all religion in the world, absolutly you know who is the religion that same with this classification and the best answer is ISLAM. ISLAM contains 3 classification that same with logic and now you have knew about true religion according by logic.
hopefully with this explanation We know which religion is the right one, thank you for your attention, sorry for all the shortcomings, Wabillahi taufik wal hidayah wassalamualaikum warahmatullah wabarakatuh.