Hi! 
I’ve saw this topic on the forum:
And I’ve got another one question: What’s the better: Xfce, MATE or LXQt and why do you think so? 
I also remembered that I used Cinnamon in Linux Mint many times ago, and I also remembered that Cinnamon crashes sometimes when Linux Mint gets some updates.
The answer depends on what you’re looking for? I don’t like either of these but it’s mostly a personal preference stemming from a usability and user experience POV than anything else.
I’m looking for a beauty and an elegance. I’m using Xfce now, but every time I needs to set up this environment for it doesn’t looks somehow like this (only if I’m not using MX Linux now) :
And I want to know: What are the cons have MATE and LXQt, and can I switch to them quietly?
Do they have all of the functions for daily working, or they haven’t something of them?
Also I know that MATE and LXQt have some customization functions those Xfce haven’t, because I used them many times ago.
So, what’s the better?
Again - this is subjective. The look and feel and how they are in each DE is different. From a usability POV, it’s really a personal preference. If any of them work for you, they work for you. If not, you can move to something else that looks better that you like to use better. For example: I prefer GNOME. It like the look and feel and reminds me less of Windows.
All these DE’s are stable depending on the distro you choose. I like Fedora and GNOME. So I use Silverblue and Workstation.
If you’re undecided try them all and choose which one you like the most! 
Thanks! If here be honestly - I’ve create a virtual machine for trying to test them all.
And there has different cons and pros for any environment:
. But I can’t open a terminal window by pressing “CTRL+ALT+T” 
cd command for navigating through directories.Maybe you could check this post: https://askubuntu.com/questions/1243734/how-do-i-rebind-the-keyboard-shortcut-to-open-the-menu-in-lubuntu-20-04.
By default looks ugly (at least for me too), but you can get started into ricing it, but ricing requires some technical knowledge.
What do you exactly mean by that? I’m not sure if you’re talking about the “Open terminal here” button when you right click in a file manager. If it’s that maybe you have to add that option in your file manager’s settings. I think comes by default in Thunar, which comes generally installed by default within XFCE.
There’s an instruction for creating your own themes, right?
I’ve been using Cinnimon (Mint) and it’s been working for me after a few tweeks to regain things I lost moving from Windows.
Kubuntu’s VM effed up the Windows host, so I have moved away from that. But that’s a Me thing.
Creating your own theme is not exactly simple, it requires some coding and/or at least dealing with GTK’s CSS.
I know that what i’ve written above may be weird since it seems you’re new to linux, i’ll give some more detailed info on another answer.
You can switch between them indeed, but it might get a little messy because:
If you need some help with installig themes feel free to ask.
MATE and XFCE are pretty similar in terms of features, and they both use GTK 3.
All of them have pretty much all the functions you will need. Desktop environments don’t make that much of a difference in the long run. What anables you to work are your applications, if they work, them you can work no problem.
Why does this matter? Choose what you want to choose. All are great options.
From where can I download some themes?
So, LXQt is the coolest choice for me now 
. It looks nice out of the box, and has every tools for daily working. The worst choice for me - MATE. It doesn’t looks so nice, and hasn’t some tools for daily working. Xfce - in the middle. It has everything you’ll need, but it doesn’t looks so elegance.
From a security perspective, none of these desktop environments default to Wayland and instead still use X11, which suffers from abysmal security. Vanilla GNOME (without extensions) seems to be the most secure option at the moment, with Plasma expected to trail close behind in the near future. If you need to use something lightweight, Sway might be the next best option, but because it’s a tiling window manager it shouldn’t be recommended to the average Joe.
If you still need to pick a lightweight yet intuitive desktop environment, the next best thing would be to pick whoever is most ahead in adopting Wayland. I’m not 100% sure, but based on the Linux news I follow, I believe out of these three LXQt is the furthest along in Wayland adoption and Xfce is notably behind in progress.
TL;DR if you want to prioritize security, pick: Vanilla GNOME > Plasma > LXQt > MATE
This ranking will surely change or even out in the future as things inevitably improve over time.
Even Sway doesn’t use the screencopy protocol AFAIK. Not to mention the default wlroots portal implementation kind of sucks. Nowhere near as feature rich as GNOME’s portal.
That is typically correct, though secureblue’s Sericea image (using Sway) apparently secures privileged Wayland protocols. Even without it, using crappy Wayland implementations should still be preferred over X11. At the moment everything falls behind GNOME, so if someone is unable to use GNOME it’s a matter of picking what is “relatively” better.
If you wanna customize your desktop you can check some icons,wallpaper,log in display most of the youtubers are sourcing their customization here here at pling..
Some decent wallpapers here. at Wallhaven
And for tools, distro’s have different default applications/some are vanillas, so its good to start learning how to install them and taking some notes for an app of your choice 
.Also take a research before adding them on your desktop.
In my case XfCE revived a 15 yo laptop to perform vastly strong. It was cracking down under demands of win10 and after beeing freed it just prospers 
Forgive the delayed answer, but luckily @Squash has given you a good one already. Just to complement, I’ll suggest the themes by Vince, a designer that makes, and updates to this day, great themes for both Qt and GTK applications and desktops.
You will notice that many Qt themes by Vince and by other people require something called kvantum. It is a program that changes the style of Qt apps, and makes them follow the style of the theme you install and choose.
Also, the user’s @TheDoc and @anon73303192 gave you some nice security advice regarding linux desktops. There are some terms in their posts that you might not be familiar with yet depending on how experienced you are with the whole linux thing. That’s perfectly normal, just keep calm and don’t get to overwhelmed with all of that.
Play around with linux to learn, just be careful with your data while at it, make your backups and stuff…
Also feel free to ask more questions in the forum and lurk around a bit and you will eventually learn it.
Ok. I’ll do 
But I have the last question then: Why Wayland is more secure then X11? X11 has a lot of exploits? Isn’t it safe in some cases? Or why?