Hi, Stephan.
I was tripped up in the beginning, too. Then I realized that the gestures and actions in phosh (phone shell, the mobile-adaptive version of PureOS), are different from Android and iOS. It gets easier quickly.
This thread might help with some of the copy/paste issues: Terminal to clipboard
In addition to the entire Tips & Tricks wiki that @Caliga linked, you may also want to take a look at:
Here are some apps that work reasonably well, most of which are not yet in the short, curated list in the store:
Edit: BTW, most of the Tips & Tricks were written with the previous amber repository apps in mind. Your phone is probably already on byzantium repo, so a few things might be slightly different now.