How to keep pc clean and fast as long as possible?

I heard CCleaner is OK. It can help to remove some unnecessary things on your PC.

Look for these kind of programs on forums with users that know their business. And if you see a popup for a PC optimization tool, avoid it at all cost because it's probably a scam.

Oh, and MalwareBytes should be a great malware removing tool. If that doesn't find any malware, you're probably doing things right anyway. If it does, it will surely help to get your PC fast and stable again.

Agree with CCleaner. Though be careful that by playing online games it may crash as it messes with your cache files. For instance, CSGO. But it's a safe program to use.

Ccleaner
+Defrag
+delete old files
+msconfig

I only use CCleaner. Not much else, but I do a clean Windows install every 2 years or so

Is it better to use some custom program for defrag? Or just stick with cmd defrag command?

I haven't used CCleaner and defrag utilities since I got a SSD last year (actually I think they built in Windows an auto-defrag thing since Windows 8). PC is always fast and quick, you don't have to worry about fragmentation on a SSD.

Rather than looking for "cleaners", take a preventative approach. A combination of NoScript and whatever version of AdBlock for your browser will help prevent most malware that you may encounter, assuming you have well tempered browsing habits. It terms of browser, if you're using anything other that Firefox (or other stamle Gecko forks) or Chrome (or other stable Chromium forks), change that. Assuming you're running a modern flavor (7 or higher) of Windows, Microsoft Security Essentials is surprisingly robust as an anti-malware scanner, as long as you keep it updated.

For local cleaning, most system-level activities (defragmentation, for example) are handled automatically. Locking your pagefile to a static size rather than allowing Windows to manage it will further assist, but make sure you make it large enough - if you have slack HDD space I notmally recommend RAM + pagefile =~32GB on modern systems running modern games. Sure, it's overkill, but it provides plenty of buffer. Then use built-in disk tools to clear logs/temps, then become familiar with temp locations on your PC (TEMP folders for Windows, as well as package archive locations for Nvidia/AMD) for manual purging. As a Steam user, you should also have TikiOne Steam Cleaner installed to occasionally purge redists from Steam game installs. And if you're NOT on a laptop and do not use hibernation mode, look up how to disable your hibernation file (yes, you have one) to further reduce bloat and over time fragmentation.

In terms of drivers, never use Microsoft Update for drivers. Sure, they've mostly fixed the horrible distribution errors and mismatches of the past (save a few catastrophic incidents in recent history), but it always keeps archival copies in a location that isn't always user manageable, slowly wasting space. When downloading Nvidia/AMD drivers, always choose custom install and always use "perform clean install" to avoid them doing the same.

If its freezing and not related to a hardware issue, i would run a malware scan. Scan with Malwarebytes

When I see "clean your PC" and nobody speaks about literally cleaning their PC, I wonder if ppl realize that never cleaning it is worse than most software out there xD

CCleaner helps to remove unneded temp files for more storage space and it makes it easier to erase browser data with one click for all browsers.
You can also use its registry cleaner. It can be a cause for the OS being slow in general.

The problem with Windows is that the updates jut pile up and they are the cause of OS bloating that is also a reason for slowdowns. Simply put, right now the only way to really have a stable system for a long time is to have an LTSB Enterprise Windows, but it may feel a bit barebones, almost Windows Server-like.

Also, dust the PC itself from time to time. You'd be surprised how large slowdowns can dust cause.

I actually like system mechanic as my general tool. I've never found it to screw anything up, nor slow it down, and it's pretty versatile as to what you want it to do. Instead of taking big, sweeping measures, you can use the individual tools that you wish