Microsoft Software Protection Platform Service: CPU use 30-50 %

In my Windows 10 Home, 64bit the Task Manager show a process called "Softwareschutzplattform-Dienst von Microsoft" (Microsoft Software Protection Platform Service) CPU usages at 30 to 50 % and reduces the speed of the Notebook.




And another process uses as much CPU: "windows antimalware service executable".

How could I avoid it?

These come from using Windows Defender as your antivirus (AV) solution. The only way to get rid of them is to switch to a different AV package. I've noticed that they use significant CPU resources only immediately following a boot-up (initial scan/update) or when running a scheduled activity (scan or update). Otherwise, they don't really consume very much resources, including CPU. Perhaps you can learn to live with this?
Hope this helps,
--Ed--

Many thanks, Ed.

Otherwise, they don't really consume very much resources, including CPU.

Unfortunately this somehow appears to be different here. When there are special processes like catalogizing, searching, read, scan files, folders, open folders and much more, done by some programs these defender processes run all the time as long as the processes of the programs last, if I see it right. And always using about 30 to 50 % of CPU or even more, so all the time the Notebook is slowed down.

I am wondering why that trashy Windows does something like that...well...anyway, many thanks again, Ed.

In your situation, Defender isn't helping. I'd suggest downloading and installing one of the best of the free AV packages, and then making sure Defender is indeed turned off (it should be by default, but it never hurts to check). You can get some great selections from Neil Rubenking's March 17 article for PC Magazine: The Best Free Antivirus Protection of 2017 | PCMag.com.
HTH,
--Ed--

PS: Ich bin ein Amerikaner, aber wuchs in Deutschland auf. Mein Vater war beim Armee, und wir wohnten in Kassel und Heidelberg zwischen 1956 und 1960, und dann wieder von 1963 bis 1968. Nochfals arbeitete ich in Frankfurt im Sommer 1970. Weil ich immer noch manchmal als Dolmetscher arbeite, technische Artikeln von Deutsch auf Englisch zu ubersetzen, kann ich immer noch was sprechen und schreiben, und mehr verstehen.
[Translation: I'm an American, but I grew up in Germany. My Dad was in the Army over there, and we lived in Kassel and Heidelberg between 1956 and 1960, and then again from 1963 until 1968. In addition, I worked in Frankfurt for the summer of 1970. Because I sometimes still work as an interpreter, translating technical articles from German into English, I can still write and speak [German], and understand even more [German].]

Thank you very much for the link, yes, that is a good idea to use one of those. And the last time I used a none Win anti vir program, I used Avast, the best one on that page.

Das ist ja unglaublich, ja, in der Tat, sehr gutes Deutsch.Damit lassen sich derartige Artikel natürlich sehr gut übersetzen. Also vor 47 Jahren das letzte Mal in Deutschland gewesen, ist ja schon ganz schön lange her. Ich war leider erst ein einziges Mal in Amerika, in Los Angeles, in den 90er Jahren.