As Salamu aleykum respected scholar. I'm praying salah since I'm 12 years old. But i prayed incorrectly until i turned 16(at least i think so) because nobody taught me the correct way. I'm trying to make them up but i also realized that even after 16 i mostly prayed in our house on a wooden floor that was painted with paintbrush made of pig hair. Does it mean that most of salahs i prayed in my life are invalid? Am i need to make them up? This make me very upset. I don't want to live anymore.
All perfect praise be to Allah, The Lord of the Worlds. I testify that there is none worthy of worship except Allah, and that Muhammad is His slave and Messenger.
The use of a brush made of pig hair to paint the floor does not necessitate that the floor is impure.
Pig’s hair is pure according to the Hanafi and Maaliki Schools of jurisprudence, and this is the view chosen by Shaykh Ibn Taymiyyah .
Therefore, there is no problem about this, and there is no harm on you in praying on that floor.
As regards your previous prayers, you did not clarify to us what is exactly the mistake, as it may not require that you make them up.
In any case, if we presume that you used to abandon one of the conditions of prayer, or one of its pillars, then the scholars differed in opinion whether or not you are obliged to make them up. You may act according to this view as a way of removing hardship and avoiding difficulty.
According to the view that stipulates that it is an obligation to make up the prayers, then you are only obliged to make up the prayers from the age of puberty and not from the age of twelve years old.
Allah knows best.
You can search for fatwa through many choices