changing "user profile" for specific user depending on time

RouterOS Scripting
1

i want to use a rule that controls specific user’s speed

simply , i want that user work with 256K from 9 AM to 3 AM
and with 512K from 3 AM to 9 AM

How can i do something like that?

2

With queues.

In particular, check the “/queue simple” menu. Each queue can have a time set. You’d need to create two queues - one in a range, and one for outside that range.