How to give a guaranteed speed to one client on mikrotik?

Question

Programming languages

Good afternoon.
How can a connected device (via IP/MAC) be given a guaranteed bandwidth? In the case when he needs it, he occupies it, at other times, other clients can take this lane.
I tried to do according to the instructions through Simple Queue / Tree, but absolutely nothing worked.
* I DO NOT need to limit the speed of this device or others, namely to give priority, it can take at least the entire available channel, as long as it is guaranteed to it.
Thank you!

Answer 1

I was developing web applications

I assume that you know JS, then why not choose it?
Desktop written using Electron.js
Mobile - ReactNative
Another option - C#
Desktop on .Net Core
Mobile on Xamarin

Answer 2

Use limit-at. As soon as the user falls under this queue, RouterOS begins to allocate a guaranteed speed to him. BUT if memory serves, in order for the queue to work, it is necessary to specify target and max-limit. If so, then specify max limit the entire width of the channel, in order not to limit it