Just like Windows has updates, your phone, whether it's an Android or an Apple and the Apps, need to be update. Not updating your phone is like not having your oil changed. This is free, and you can do it from home while connected to WiFi.
Software bugs and old apps can slow down your phone or make it crash. Software developers find and often fix these bugs daily. Updated versions of the Apps are free in the App Store.
The first thing you want to do is connect your phone to the Wi-Fi (wireless internet) so you don't waste your data. If you don't have home wi-fi you can connect at your local Library, and at many restaurants or work.
Then go to the App Store and update the apps one at a time or have it update all apps. Before you update an app, you can look at the app details to see what changes have been made. Note: There is always a chance the updated app may break something, so use a little caution but most often the updates are worth doing. After I install updates I test the app to verify its still working properly before I actually need to use it.
With Android the App Store is named Play Store. Your apps are listed under My apps & games.
Your cell provider also releases an OS update from time to time. When you are notified that an update is available you should connect to the wi-fi when you have time to allow it to update and install the update.