Pip Social support: changes to PIP law from 6 April 2016

Hi I got a letter asking to sign and only answer 1 question could I engage face to face April 2016 to my last assessment November 2020 i said its not changed from 2011 to present and won't change only get worse but the time they have asked I was even poorly I had 247 care n home treatment I don't now  n havent since may 2020 just a carer 2 times a week and I got awarded high on all after getting 0 on mobilty take it there paying me backpay as they said its not assessment or review its if anything a backpay ive not had my pips stopped they said about me owed backpay from April 2016 to November 2019 I did sent them back and they have recieved them n with decision maker on 17th December I was wantin to ask hw long from that point to paying me the backpay is it usally I'm askin because I had a fire in my building and my bed and some kitchen electrical were water damaged n I wasn't insured sorry if u can't understand im not the best with textin and spelling  thank you in advance for any rwplys