Wa `alaykum as-Salamu wa Rahmatullahi wa Barakatuh.

We are encouraged to learn to pronounce the words of Fathiah and essential surahs and Du’as of prayer as best as we can. The best method of learning is through a qualified teacher: As Imam Al-Bukhari said in Sahih al-Bukhari, “knowledge is attained by studying from a scholar.”

So, I would urge you to get the help of a qualified teacher; it should not take long for you to learn the basics.

In case you are unable to do so, please listen and practice by following the Mu’allim lessons imparted by famous Qari like Minshawi; you can download them here:

https://archive.org/details/tvQuran.com__Moalim-Minshawi

That is how the Quran was taught in the Maktab in the Muslim world.

As for the past mistakes, you should ask forgiveness of Allah.  The Prophet, peace be upon him, said, “Allah forgives my Ummah of their mistakes due to ignorance or forgetfulness.”

I would urge you to read the last two verses of Surat Al-Baqarah every day before going to bed. If you wish you may also read it in the morning as well after Fajr.

You may also refer to the answers posted above on similar questions.

I pray to Allah to forgive us our mistakes and have mercy on us.

Almighty Allah knows best.