The way to attain a high level of faith as our righteous forebears the (Salaf) did is, firstly, by persevering in seeking to understand what Prophet Muhammad brought, then by persevering in doing what he enjoined and in refraining from what he forbade. All of that is to be done with true sincerity, having no interest in worldly gain, and hoping for the Hereafter.

If you are losing faith in Islam, you need to increase your hope and trust in Allah. You should increase your good deeds, such as reading the Quran, giving charity, remembering Allah (Dhikr), upholding the ties of kinship, etc.

Here are some useful tips for resisting the temptation to show off: Remembering that Allah is always watching His slave. Seeking the help of Allah. Knowing the effects of showing off and how it will be judged in the Hereafter. Thinking about the punishment in this world for showing off. Concealing worship and not making a display of it.

There is no Islamic explanation for Déjà vu, and it is not discussed in the Quran or the Sunnah, or by any of the scholars of Islam, and it has no connection to any of the fundamental or basic teachings of Islam.