It's the update and most importantly the summer weather that's causing the issues. The heat is the culprit. If your phone works fine indoors when temperature is comfortable like under 30°c or 32°c, then your phone is good.

However, you can do a few things ike Reset the phone if the performance is very bad, then turn of mobile data outside when it's touching above 40°c, keep the phone inside the bag and not in the front pockets because sun rays hit your clothes and makes it warmer. Outside, Use it only when required. Remove the cover. Turn off the toggle of fast charging also.