iPhone lagging and very slow

this is not necessarily a very answerable question but my iphone has been terribly hard to use it’s been so glitchy i can’t even text people normally. i got this phone under a year ago and its kind making me mad. my mom doesn’t have the money to buy me a new phone. my family doesn’t have money and i was lucky enough to even have an apple phone. im not sure if this problem could be caused by the rumor that apple slows down your devices and makes them run slower? it’s something like that. i’ve seen people on social media have the same problem especially with the ios16 update like the battery running lower and stuff. my phone is very cracked on the top right corner and the front camera. the left and bottom are fine but anything mid right to top i can’t even interact with. i’m planing on getting it fixed somewhat in the next couple days. my question mostly is that is there any possibilities that i can do something to stop the lagging? i really can’t buy a new phone and this phone isn’t that old.

[Re-Titled by Moderator]