Seems I solved it, many thanks to all contributions in this thread! Sorry for posting an extra answer for this instead of a command but in a comment I cannot illustrate with pictures how I solved it. Furthermore I had to post one big picture containing 3 screens because SE prevents posting 3 pics with low reputation.

Concerning the solution: Checking if the package was in yum (which is dnf now) was they key. (Step 1 in the pic) The command is: dnf search packagename (of course you have to replace the word packagename with your search key word.

Then I installed the package which I have marked and it was succesfull (Step 2 in the attached pic).

Afterwards I checked if the package is really installed (Step 3 in the pic, like it is described here (yum - check if package already installed)

Seems I solved it, many thanks to all contributions in this thread! Sorry for posting an extra answer for this instead of a command but in a comment I cannot illustrate with pictures how I solved it. Furthermore I had to post one big picture containing 3 screens because SE prevents posting 3 pics with low reputation.

Concerning the solution: Checking if the package was in yum (which is dnf now) was they key. (Step 1 in the pic) The command is: dnf search packagename (of course you have to replace the word packagename with your search key word.

Then I installed the package which I have marked and it was succesfull (Step 2 in the attached pic).

Afterwards I checked if the package is really installed (Step 3 in the pic, like it is described here (yum - check if package already installed)