Technology independent Write the project some database ideas

I don't know how to design a database for a forum.

Let's just do this.

User table

+----------+--------------+------+-----+---------+----------------+
| Field | Type | Null | Key | Default | Extra |
+----------+--------------+------+-----+---------+----------------+
| user_id | Int (10) | NO | PRI | NULL | auto_increment |
| Username | varchar (255) |     YES | |                NULL | |
| password | varchar (255) |     YES | |                NULL | |
| Mobile | varchar (11) |     YES | |                NULL | |
| Address | varchar (50) |     YES | |                NULL | |
| sex | varchar (10) |     YES | |                NULL | |
+----------+--------------+------+-----+---------+----------------+

The table

+------------+--------------+------+-----+---------+----------------+
| Field | Type | Null | Key | Default | Extra |
+------------+--------------+------+-----+---------+----------------+
| room_id | Int (10) | NO | PRI | NULL | auto_increment |
| user_id | Int (10) | NO | MUL |                0 | |
| Room_words | varchar (255) |     YES | |                NULL | |
| Room_title | varchar (100) |     YES | |                NULL | |
+------------+--------------+------+-----+---------+----------------+

Words table

+---------+--------------+------+-----+---------+----------------+
| Field | Type | Null | Key | Default | Extra |
+---------+--------------+------+-----+---------+----------------+
| word_id | Int (10) | NO | PRI | NULL | auto_increment |
| user_id | Int (10) | NO | MUL |                0 | |
| room_id | Int (10) | NO | MUL |                0 | |
| Words | varchar (255) |     YES | |                NULL | |
+---------+--------------+------+-----+---------+----------------+

User table doesn't mean anything.

The table

ROOM_ID is the unique identity of a post that a person publishes

USER_ID is the only sign of that man.

Room_words is the supplementary content of the first floor of the post
Room_title is the name of the post.

And then

Words table

WORD_ID's unique identification of the words of reply
USER_ID the unique identity of the person who replied
ROOM_ID the unique identification of which Post replies
Words specifically replied to what the words

Honestly, all the responses were put on a sticker that made me panic.

Feel the database should not be designed like this

So write and ask for advice

Technology independent Write the project some database ideas