Track simultaneous selection issue

Hi I have a problem using Cubase 10 Pro.
I think I can get help. Leave a comment.
As you can see in the picture, I did not click on a region at the same time,
but I automatically selected two regions,
which are not set as a group track separately.
How can I get rid of that?

Hi and welcome,

Make sure the MIDI Parts are not grouped. If the are, you would see a group icon in the right top corner of the MIDI Parts. To Ungroup it use menu Edit > Ungroup or the Ctrl/Cmd + U Key Command.