12:106

وَمَا يُؤْمِنُ أَكْثَرُهُم بِاللَّهِ إِلَّا وَهُم مُّشْرِكُونَ

Sahih International

And most of them believe not in Allah except while they associate others with Him.

Bangla

অনেক মানুষ আল্লাহর প্রতি বিশ্বাস স্থাপন করে, কিন্তু সাথে সাথে শিরকও করে।

My Critical Reasoning:

What type of Ayah it is?
Statement containing information
What is the statement about?
Believe and shirk
What is said about belief?
That most of the people believe in Allah
What is said about shirk?
Most of the believers are Mushrik! Inna lillahi wa inna ilaihi rajiun!

Can you derive any other meaning out of it?
We actually cannot conclude from the Ayah whether it meant by ‘most of the people’ as ‘all human being’ that believe in Allah but the obvious meaning should be that among those who believe in Allah, most of them are Mushrik.
What does that suggest?
If we take the mention of ‘Allah’ here as a ‘God’ or as ‘Creator’ then that means most of the people who believe in a God or a Creator are Mushrik. And then that includes all those religious people out there who believe in a ‘God’ but are Mushrik such as,
‘Hindus’ who believe in ONENESS of God but are Mushrik
‘Jews’
‘Christians’
‘Zoroastrian’
etc.
Then if we take ‘Allah’ as a literal meaning to Allah’s name, then that includes only to Muslims who believe in Allah but most of them are Mushrik.
Therefore, whatever meaning we derive here for ‘Allah’ it is obvious as the Ayah confirms that most of the people whether believe in a ‘Creator’, or a ‘God’ or ‘Allah’ are actually Mushrik.
What’s my relationship with that?
Scary information! Need to check how and what acts make a Muslim as Mushrik.
But isn’t it clear that Grave worshipers are Mushrik, that we already know? I mean. most of the Ulema say that!
Well, it is. But they are not many or doesn’t involve the ‘most’ ! Allah says ‘most of them’ who believe in Allah are Mushrik. Therefore, most of the Muslims are Mushrik too! Inna lillahi wa inna ilaihi rajiun. That can’t let me sleep until I know who are Mushrik?
Doesn’t Ulema already tell you who are Mushrik?
Seems it is not as easy as you thought!
What do you mean?
Let’s analyse. If you go by sect or by groups of all Muslims, each group is headed by Ulema and that in general makes most of these Ulema also Mushrik! Inna lillahi wa inna ilaihi rajiun. You will usually hear about sects that there will be 73 sects in Islam, only one will make to Jannah and rest are for the fire! That obviously makes ‘most of the people’, so you might think the problem is solved. But no!
Why not? 
Because all of these sects think that they are the saved one! Because they claim to follow the Quran, Hadith and the way of the righteous Khalifah!
How it could be?
Very easy! I will mention the vast Mushrik scenario in most of the people you know around you.
Even the Grave worshipers (of course, it is their Ulema) derive the evidence from Quran,
The scholar that preach “Govt’ doesn’t impact on the mind of people, it’s media and philosophers” also derive logic and reason in support of his acts and arguments of how he takes away people from longing and struggling (Jihad) for “The Khilafah”
and then the groups, ‘Islamic’ political parties engaging Muslims in shirk (voting and engagement in ‘democracy’ that exists today) They also think they are the saved ones!
Therefore, because they gave evidence from Quran and Hadith, you would never think or have the least idea that their actions could constitute the elements of shirk. You would never give it the slightest chance that these Ulema could be the one who are Mushrik and calling people from the gate of Jahannam!
That scares me to death as if my heart stopped breathing, these are the most popular Ulema today, they have millions of followers, they have thousands of lectures!
Well, they have most of the things correct and according to the Quran and Saheeh Hadith but even they have 99% things correct of what they preach and you, of course, will get benefit from their wisdom but shaitan just need one thing to make them Mushrik, the slightest link that constitutes element of shirk to make the way of the most learned Ulema and their follower to Jahannam! So, don’t forget the power of shaitan when Allah says shaitan even tries to manipulate with prophet’s recitation of Allah’s words. So, who are these Ulema that shaitan cannot touch their word? Maybe in a particular moment, shaitan has overpowered them and they might later reaslise their mistake. Allah knows best. May Allah guide them. They used to be my most beloved learned brothers and Ulema of this time. If my knowledge and intellect are like a leaf, I consider their’s like a banyan tree. But I found many other “not a popular at all” Ulema go with my understanding that the slightest relation with democracy and voting is shirk!
I think one should not rely on his Path to Jannah with Ulema!
Well, they are the most learned ones!
But then they lead their people to Jahannam!
That’s actually right and was warned about! in Quran and in Hadith
So what we do? What’s the way out?
You have to read and think hard (As Allah questioned many times, “don’t you think”?) and don’t be settled that you are saved (that you follow your most learned Ulema and you think he gave you a ticket to Jannah.)
Read yourself the Quran and Hadith and think about it yourself first.
And then you check with Tafsir (as most of those are, apart from the reason or incident of revelation, merely opinion and understanding of that Ulema who has written the tafsir, therefore, by reading tafsir first you already are giving your mind to someone’s understanding which will limit your thoughts)
And read other great scholars explanations such as Madhab (school of thoughts)
And read books from Ulema and read or listen to contemporary Ulema
and then see which one goes with your understanding! And that’s how you are protected and know that you are not thinking ‘wildly’ and going ‘astray’ as they discourage you to read (by the way, the ones discouraging you to read yourself and think, you already can understand that probably these are those Ulema who you need to cautious about as they want you to follow only their’ Ulema and discourage you to think)
But when you read yourself, you might make mistake and come up with a wrong decision (even after aligning your understanding with few Ulema, as mentioned before) but that will at least give an advantage in your case before Allah, the Most Just on the day of Judgement! If you struggle to find the right course, you can have an argument with your Rabb on that day,  “Oh my Rabb, I tried my best with the intellect you gave me, I never rest, I never wasted my time, I was constantly thinking on your Ayat, you are my witness, your Mailakah are my witness so save me from Jahannam” And your Rabb is never unjust! (You can start pleading and crying right now as it makes me!)

But how I know which acts are the acts of Mushrik and how we do it?

We have to look for the evidence from Quran and Hadith what actions are regarded as the act of shirk! So, keep reading!
And Allah knows best. May Allah give us the correct understanding of His Deen and protect us from Jahannam! Ameen.