This is probably a problem best sorted by showing the problem to someone who knows what they are doing so that they can show you what to do to fix it. Maybe try the shop where you bought the phone from? Trying to sort issues like this using words on a forum could be confusing and complicated. I am not being patronising here. I truly believe that some problems need to be seen to be understood and fixed.
Huawei Mate 20 Pro review: In-depth hands-on