Almost no need to quote, but any way,
Additionally I took a look at /var/log and for example, in "/var/log/messages" there are some errors, but looking them online hasn't payed off since there is no info available for them. On the other hand, the OS seems to work fine and I can't say that I have some problem with it up to now.
So what exactly is the problem ? You say: ""/var/log/messages" there are some errors, ",
But neglect to say what the errors are, or what the error messages say,
And "some problem",

Don't you think it would help us, if we knew exactly what the "some problem" is ?
You might want to take a look at this:
https://www.debian.org/intro/why_debianand also
https://wiki.debian.org/DontBreakDebiaAdvice For New Users On Not Breaking Their Debian System
Debian is reasonable stable, but how long it stays that way mostly depends on how well the system administrator manages the system.
I suppose , also a factor would be if the system administrator knows about syestemd , what it is , and how it effects the system.
Systemd has been in use now for about 3 years now, but in relation to the older system V it is fairly new, there is some question as to how stable it really is, only time will show on that. It does seem stable, but for some of us "old school" I guess they would call it, any way, some system administrators do not trust systemd that much, most end users do not even notice or know the differences.
compared to e.g. Ubuntu there's no trademark appearing when I boot the OS or when I turn it off.
Trade mark , and graphic 'branding' and logos have nothing to do with stability or reliability, another example,look at MS windows, totally unstable, and unreliable, and as you said,
but having a lot of trouble in the past with other distros,
Ubuntu is another good example, the trade mark, does not make it any more stable, or reliable, and I certainly would not trust Ubuntu on something where stability , and reliability are concerned.