Facebook is great and powerful social media, every minute million of peoples account are login, sometimes server goes down.
and so many factors affecting in login issue,
yet you have tried to turn off and turn on your mobile data and wifi.
once try this and then try to login account,
otherwise follow other methods
It is depend on mobile network, cookies and cache you need to clear all junk cache which affecting here.
1st try turn off and turn on mobile data then this.
it will available in your mobile inside > storage or advance settings.
Inside application manager > find Facebook go inside application and go to storage and then clear data or cache,
1st clear only cache try to login, if still facing issue then clear data and try again.
You need to set new one password to forget it.
Go to Here
Enter Your Email or Phone Number There and search it!
You will Receive Code In Email Or Phone number
Enter There Code And Continue It.
Set your password always strong to using special character.
You are sure your email and password is correct but still facing trouble in login, Clear cache and cookies of chrome.
1. Go to Right Corner in Three Dots (menu)
Then go to below > Settings
Go Below Open Advance
Clear Only Cache and Cookies Data
How To Resolve Facebook Login Problems
You should also report to Facebook for login issue, in this case Facebook support stuff will try to help you.
Just you sent them your trouble here