As an 11 year old now, I understand a lot of what my parents used to tell me when I was a little kid and I now feel that we as Muslims should not celebrate Halloween and here are my reasons for that
Number one, Halloween has Pagan and Christian roots and involves celebration of superstition, black magic, and devil worship. As Muslims we only believe in Allah (SWT) and pray to HIM. Celebrating Halloween would mean praying to Shaytan, which we absolutely cannot do. Also praying to anyone else but Allah (SWT) would be like doing shirk for which Allah (SWT) will never forgive us.
Number two, we are pleading and tricking people for candy. Our Prophet Mohammad (SAW) absolutely did not like begging and advised people to not do that. So going trick or treating means that you are doing something, which our Prophet Mohammad (SAW) did not like. So we should not do any such activities that would make us bad