My iPhone storage is full

I got iPhone 7plus with 256g memory storage

and my phone started working so slowly

i got notification that my iPhone storage is full

i just have some photos and videos thats take 4 gigabytes

and when i scroll down i see that system data it’s taken 226 gigabytes of the memory

could you help me please

my phone working so slowly

i don’t understand why.

[Re-Titled by Moderator]