When I was younger I used to do my prayers very very fast and I don’t know if they’ll be counted as prayers or not. I also don’t know when I hit puberty as I started praying before the age of puberty. Thirdly I have forgotten how many times I have done this in the past. I’d like to know if it’s obligatory for me to make up these prayers and if so, could you advice me on how to do it?

You do not need to redo your prayers unless you know for sure that you did something to invalidate them