the new iphone update has made my phone very laggy and causes the battery to go down a lot quicker

Both those behaviors are expected momentarily after an update. Your iPhone has to work a lot harder to complete post-update tasks such as updating apps and as a result it can run a bit slower and drain more battery. Give it a few days and it should return to normal. In the meantime which can help, perform a Forced Restart.

• Press and quickly release the Volume Up Button
• Press and quickly release the Volume Down Button
• Press and hold the Side Button until you see the Apple Logo 

(If performed correctly, you should only see the Power Off slider, not the Emergency SOS/Medical ID slider. But don't use the Power Off Slider, keep holding past that until the screen goes black and the Apple Logo appears, which can take up to 30 seconds.)

In addition to what Zachyy suggested, what is your Battery Health? Settings > Battery > Battery Health - if it is near, at or below 80%, the useful life of the battery has been used and it's time to pay Apple to replace the battery in your phone. Batteries don't last forever as they are consumable parts.