Well, there are hundreds of question now. But, let’s explain some basic things. Databases run in C or C++ and are extremely fast. If you were to write your text processing in C then, yes, it will run fast enough to put onto a webpage. But, you would need to wrap it up in odd libraries to get it all to work correctly. A ton of work when PHP is designed to do all of this work, for you.
Next, database code is extremely fast if the database is designed correctly. For simple posts, it is extremely flexible and very fast. That is why every huge website in the world uses it. Connecting to a database is easy, just a couple lines of code, reading, storing, updating and deleting data is easy to handle. The only tricky part is to layout your needs for data first and design the database tables to work best for your useage. I suggest leaning PDO since it is the most secure. It is basically an advanced version of MySQLi. If you use PDO and “prepared statements”, your site will be quite secure from hackers. Also, you need to design the database tables so that they interact with each other. For example, if you have users in one table and posts in another, you can link them together using DB-Join’s. In a query, you can join two tables to make the search for data faster. Such as finding all of the latest posts for one user or all of the latest posts for all users. Simple queries.
Now with that said, think of a database a a spreadsheet. It simply has pages ( tables ), rows of data and columns of fields. Simple. And, you create a name for each field and a name for each table. All “data” needed for users would, of course, be saved in a table named “users” or “members”. All posts could be saved in a table called posts. Simple enough. In the posts table, you would have one field called, let’s say “owner_id” or “poster_id” and that links them back to the users table. So, in one simple joined query, you can pull out all the details of any user along with all of their posts. For programming systems, you might want to have users, program_snipit’s or whatever…
A site that has a ton of general information is here: https://www.w3schools.com/sql/ On the top, you can select the language you want details about and on the left a subject inside of that language. It has PHP, CSS, HTML and PDO to get you started. The code they show there is not always the best, but, it will get you started nicely. Also, if you want to learn how to use PDO, you should read this PDF: https://phpdelusions.net/pdo
But, I suggest you first make a list of all the data or info you wish to save. Figure out what tables the data needs to be in. Do not duplicate data at all. Make a list of tables and fields needed and how each table will work with the others. Then, have the group here review it. We have a large number of expert programmers here and can give you solid input on your design. If it is something private, you can private-message some of use to ask for private help. But, in general we do not care what you are creating, but, we want to help you with the code. Yes, it’s ALL ABOUT THE CODE ! Ha! Hope this helps get you started !