Problems in KDE

I have installed 12.1 and have updated to 12.2.
In both distributions I have problems with the windows in KDE, the do not show the top line menu e.g. to close windows of KDE. The entire windows handling in KDE is very cumbersome, the only chance is to work with the keyboard.
I have a i586 32 bit version, the processor is a Celeron.

What the best way to get proper windows working in KDE?

Thanks in advance.

And your graphics device is…?

If by top line menu you mean the title bar, it sounds to me like kwin is not running. You can try starting it in a terminal with

kwin

or

kwin --replace

See if that helps, and note that if you close the terminal window kwin will also close and you will return in the no-titlebar state.

yes, kwin was not started. The title bar is now visible and I can move the windows etc. Thanks a lot for this tip.
When I started kwin, I have received in KDE an error prompt <We are sorry. KWin closed unexpectedly>. But the title bar works!!!
In the terminal there is a steady message kwin (21556)/kdeui (KNotification) KNotification::slotReceivedIdError: Error while contacting notify deamon “Not connected to server”
Indeed it is a very old graphical card, Intel, i845, 2D driver: Intel, 3D driver: unknown classic (8.0.4)

I am quite new in this forum and working with Linux, so sorry for this basic question, in which config file could I join the command kwin --replace to executet durinmg the boot session?

By default kde effects are usually enabled
Go to the System Settings and Desktop Effects and uncheck it if it’s checked
Then logout and in

FYI: You should always be logging in manually, not using auto login.

Thanks a lot for your support, finally it works perfectly, I have added kwin --replace to /etc/init.d/boot-local