Hi Gnx74, welcome to the forum 
To let people help you it is essential to provide more information about your issue. Please read this post how to provide the info. You seem to have 2 issues:
- Install parallel tools fails
- Change resolution
These might be related, for now only you know 
For the first, are you using the add/remove software tool or a cli install? Do you have the error or log output to share?
For the second, how are you trying to change the resolution? And what is the output of xrandr & inxi -Fazi