Home network setup via hAP lite

Greetings, guys.

First of all I want to apologize in advance since I am below MikroTik beginner, but I really need to present the situation I am in with my hAP lite and home network. I am sorry if this is just another topic of ‘‘I have a problem…" and "please, help’’. Will wait for possible solution and ideas as long as it is needed.
So, I have a MikroTik RB941-2nd-TC hAP lite which my friend set it up for me. My friends knowledge of MikroTik routers is limited (but far bigger than mine), so there is no help from that side no more. I have tried to boost the hAP light a bit in terms of creating separate WiFi network for my house guests (you know, like a restaurant/cafe style) but I have failed even after carefully following tutorials. It is about me and my lack of basic knowledge of IP/TCP protocols and other staff…

What is the current situation?
My internet connection is fiber 100/10.
I have my hAP lite set to be Wi-Fi router and modem connected to fiber via Ethernet cable. Most of my apartment has WiFi signal. I have connected my desktop PC and Nvidia Shield TV (these 2 are my main devices in da haus) via ethernet cable to hAP lite and it works perfectly, having the fastest possible connection limited only by my internet dealer package.
But besides these 2 devices I have 2 more laptops and 5 android phones that are regularly connected, not all at the same time, but 4 android phones out of these are almost constantly online (usually media content).
WiFi signal can not reach 2 rooms because of concrete walls and they are more around 10 meters away from hAP lite. If I move my hAP lite closer to those rooms than I can not connect my 2 main devices with LAN cable (organisation of rooms and stuff is not easy to explain and I would bother you even more) and connecting those 2 devices via WiFi is not an option (I need constant ping on my desktop PC).
On top of that, my WiFi network has some limitations, maybe I did something wrong while trying to setup separate WiFi guest network. So most of my WiFi devices will not get more than 5/1 even if there is only 1 device connected (I know how to check devices that are connected to my WiFi, at least that), where it it is phone, that it can get higher speed (10/10 for example), but laptops (on windows 10) won’t beat 5/1.
On top of all that, I live in a huge building with over 30 different wi-fi networks in my range. Fortunately,hAP lite is set to a frequency that not a single of these networks are using.

Sorry for being so detailed and bothering.

What I want to achieve?
I want to make my home network better. But in what way?
First of all to make those 2 back rooms to be able to have constant internet connection if possible cable and WiFi.
And I want to keep current setup of by cable connected 2 main devices.
And want to make WiFi guest network separate from my own home WiFi with limited internet speed and stuff, but

I wonder if it is possible to install another hAP lite which will ( I buy and install in those back rooms), set and connect it via WiFi to my original hAP lite, so that this second hAP lite will be used like extender or bridge or AP or what ever should I call it. And than to make it possible to connect devices via WiFi and cable (possibly another desktop PC and Nvidia Shield) in those back rooms.

I am sorry if all I wrote in this topic sounds stupid.
Thanks in advance.

Have you considered a mesh WiFi AP system that connects back to yours hAP lite?

I just recently bought a hAP lite and I’ve noticed the wireless coverage isn’t amazing (though that’s not what I bought it for) so perhaps it’s that?

Hi,
try changing your wifi channel width to 20 which will give you better range but u ll lose speed

Thank you, guys for your responses.

It is not only Wi-Fi signal that I need. There comes 4 devices that needs to be connected by wire for constant connection and with minimum lag. On top of that is good Wi-Fi.

Mesh Wi-Fi would provide good cover for wireless, when combined with my hap lite. But I am not sure it will solve me the problem of having these 4 devices connected by ethernet cable…

I am getting close to buy another hap lite and combine those 2 - one to be as it is now - modem/router and the other one to work as an extender or bridge giving Wi-Fi and a possibility to connect 2 more devices by cable. I am just not sure if it is possible to set up in that way. Besides I do not get the difference between extender or bridge. I suppose extender will not have a function to connect devices via wire, right?