Hi iPhoneUser4444,
It seems you have some concerns about the battery life on your new iPhone SE. Per the iPhone SE tech specs page on apple.com:
Lasts about the same as iPhone 8
Video playback:
Up to 13 hours
Video playback (streamed):
Up to 8 hours
There are a handful of other factors that contribute to the battery usage, such as brightness, internet usage, notifications and other background activity. Some more information can be found on this support article.
Get help maximizing battery life
Notably, check out the 'Check battery usage' section, which gives guidance on using the Settings > Battery screen. The blue meters indicate how hard the phone was working during a timeframe, while the green bars represent the battery charge level for that time of day. There may be a mixture of multiple apps working simulatenously and not just Facebook browsing. These battery metrics should have a counter for how background activity each app has used in the last 24 hours, up to the last 10 days. I hope this helps you get the most out of your new iPhone SE.
Thanks for contacting Apple Support Communities.