Here are some lessons of tawheed from Qurʾān and authentic aḥādīth.
And those who take protectors besides Him [say], “We only worship them that they may bring us nearer to Allāh in position.” – Surah az-Zumar 39:3
Or have they taken other than Allāh as intercessors? Say, “Even though they do not possess [power over] anything, nor do they reason?” Say, “To Allāh belongs [the right to allow] intercession entirely… – Surah az-Zumar 39:43-44
… Who is it that can intercede with Him except by His permission? … – Surah al-Baqarah 2:255 [Ayat al-Kursi]
… Say, “Then have you considered what you invoke besides Allāh? If Allāh intended me harm, are they removers of His harm; or if He intended me mercy, are they withholders of His mercy?” Say, “Sufficient for me is Allāh; upon Him [alone] rely the [wise] reliers.” – Surah az-Zumar 39:38
And warn by the Qurʾān those who fear that they will be gathered before their Lord – for them besides Him will be no protector and no intercessor – that they might become righteous. – Surah al-An’aam 6:51
And how many angels there are in the heavens whose intercession will not avail at all except [only] after Allāh has permitted [it] to whom He wills and approves. – Surah an-Najm 53:26
Say, [O Muḥammad], “Invoke those you claim [as deities] besides Allāh.” They do not possess an atom’s weight [of ability] in the heavens or on the earth, and they do not have therein any partnership [with Him], nor is there for Him from among them any assistant. And intercession does not benefit with Him except for one whom He permits. … – Surah Saba 34:22-23
… and they cannot intercede except on behalf of one whom He approves…. – Surah Al-Anbiya 21:28
And do not invoke besides Allāh that which neither benefits you nor harms you, for if you did, then indeed you would be of the wrongdoers.'” And if Allāh should touch you with adversity, there is no remover of it except Him; and if He intends for you good, then there is no repeller of His bounty. He causes it to reach whom He wills of His servants. And He is the Forgiving, the Merciful – Surah Yunus 10:106-107
… Indeed, those you worship besides Allāh do not possess for you [the power of] provision. So seek from Allāh provision and worship Him and be grateful to Him. To Him you will be returned.” – Surah al-Ankabut 29:17
And who is more astray than he who invokes besides Allāh those who will not respond to him until the Day of Resurrection, and they, of their invocation, are unaware. And when the people are gathered [that Day], they [who were invoked] will be enemies to them, and they will be deniers of their worship. – Surah al-Ahqaaf 46:5-6
Is He [not best] who responds to the desperate one when he calls upon Him and removes evil and makes you inheritors of the earth? Is there a deity with Allāh? Little do you remember. – Surah an-Naml 27:62
Narrated Abu Huraira (may Allāh be pleased with him): The Prophet ﷺ said, “On the Day of Resurrection Allāh will hold the whole earth and fold the heaven with His right hand and say, ‘I am the King: where are the kings of the earth?'” – [Sahih al-Bukhari Vol. 9, Book of Oneness of Allāh, Ḥadīth 479]
Ibn ‘Abbas (may Allāh be pleased with him) narrated: “I was behind the Prophet ﷺ one day when he said: ‘O boy! I will teach you a statement: Be mindful of Allāh and He will protect you. Be mindful of Allāh and you will find Him before you. When you ask, ask Allāh, and when you seek aid, seek Allāh’s aid. Know that if the entire creation were to gather together to do something to benefit you- you would never get any benefit except that Allāh had written for you. And if they were to gather to do something to harm you- you would never be harmed except that Allāh had written for you. The pens are lifted and the pages are dried.'” – [Jami` at-Tirmidhi Vol. 4, Book of The Description Of The Day Of Judgment, And Ar-Riqaq, And Al-Wara’, Ḥadīth 2516 (Hasan Saheeh)]
This is only the list of ayahs from Qurʾān and authentic aḥādīth, we have not explained them. But we request you to read more translations, read the ayah (arabic) and authentic tafseer of the ayah. Contemplate on these text.
Lastly, I would like to warn you, if you die while you were upon shirk, all of your deeds will go to waste.
And it was already revealed to you and to those before you that if you should associate [anything] with Allāh, your work would surely become worthless, and you would surely be among the losers.” – Surah az-Zumar 39:65
Remember! There are many who say “Laa ilaaha illalah” but they commit shirk in their actions. So, you should never feel you have passed the test until your last breath. Continue invoking Allāh (and Him alone) and put your efforts to learn tawheed. Remember! Shaytaan, our clear enemy has taken oath with Allāh that he will mislead us except the chosen ones (whom he has no control over)
[Iblees] said, “By your might, I will surely mislead them all. Except, among them, Your chosen servants.”
[Allāh] said, “The truth [is My oath], and the truth I say. [That] I will surely fill Hell with you and those of them that follow you all together.” – Surah Sad 38:82-85
May Allāh guide us to the truth and keep us steadfast and enter us in to loftiest places in jannah – Jannat al-Firdous. Āmeen