How to make a javascript photo slider with buttons

Question

I am unable to make a photo slider despite the code having worked last year. Today it doesn't work
https://code.sololearn.com/W9vEE4P9KSGR/?ref=app

Answer 1

https://www.sololearn.com/learn/JavaScript/2760/

It was already covered in the javascript tutorial.

Go through it

or you may also see my work .
https://code.sololearn.com/WvU9e7PSeRxk/?ref=app