How to make website with users To you can login I now how to make to write username , password and submit button

Question

And how to save it and make user
Like on instagram or facebook

Answer 1

Is this just a learning exercise, or are you creating a professional website you don't want hacked?

If it's the latter, then don't bother coding it yourself but instead use a framework that does the login functionality for you. This is:
a) easier
b) more secure

Answer 2

prepared statements to avoid sql injections

Answer 3

you need to learn how to design a website, design in paper then find the keyword in google such as "make login with php" it simple tutorial for you to learn how to make login

Answer 4

If you're not an expericiend programmer, with great experiences on both server and user side web development, I will advice you to use Wordpress or any other CMS (content manager system) which are already done the lot of complex coding required to reach your goal...

If you're relatively experimented at server sided programming languages and database handling, you could try to write your own CMS/website through the use of advanced frameworks available for most of coding languages ^^