I would like to ask that when I was about 8 or 9 years (when I became baligh) I did not realize that I was doing some mistakes in my namaaz , until later I came to know that I was making mistakes, and immediately I rectified those mistakes . e.g, I used to recite tashahud and salaam together in 2nd raka of 3 and 4 raka namaz, but I rectified immediately when I came to know my mistake. Now I don’t remember how many days I prayed like that? What should I do?

If you didn’t know before then you should be ok and there’s nothing you need to do