Question about Linux?

I want to install a Linux on my (somewhat older, too weak for Win10) laptop.

1.) Which distribution would you take for normal work.

2.) I'm not a Linux expert. Is there anything to consider? Does anything have to be done regarding malware protection / security?

It is best to use a widespread distribution, such as Ubuntu. Then you also get simple support. Here's something to read:

https://mobil.pcwelt.de/ratgeber/Die-richtige-Linux-Distribution-fuer-Einsteiger-Betriebssystem-Vergleich-9780612.html

And what about point 2?

Linux mint - is easiest for beginners mfg.m.

That would be a bit more extensive to explain, but I have something to read:

https://www.heise.de/...85535.html

To 1.:

If you come from Windows and the laptop is not as powerful: Linux Mint 20.1 Xfce, Manjaro Xfce or LXQt, Xubuntu 20.04.1.
They are initially structured like Windows (taskbar below, start menu, etc.) and are well suited for "weaker" hardware.
Unfortunately not as pretty as KDE or GNOME. But that's what it works for.
How old is the device ~?
If the device can take a little more, then the above variants with KDE or GNOME. There's a little more eyecandy and functionality included.

To 2 .:

Not more than the previous one:

Don't open any dubious pages, don't click every email attachment or link.
You don't need antivirus software - it just creates more gaps in the system than it repairs.
Check for updates regularly (at least once a week).

I only have - albeit good - experience with Ubuntu (for a good 5 years on an Acer 5749z - for a year with an SSD: what can I say… System booted up in 6 seconds and ready for use)

Linux Bodhi - this is an Ubuntu derivative. Runs great on less powerful and older computers.