fuck: on the last run i did not enable sim card in volla os and now almost finished setting up all apps in sfos, i’ve realized no mobile network, due to no simcard.
so important: do not skip the step to enable and check sim card !!
final flow:
flash gigaset rom using sp flash tool
i did that on windows due to usb drivers for mtk
flashing rom was easiest on windows
tryout sim
enable dev mode (about phone-> build number 7times)
enable usb debugging
flash volla using ubports installer
this again worked fine on windows (but can be also done on linux)
test sim
enable dev mode
enable usb debuggin
flash sfos using ubports installer
that worked best on linux (windows did not want to get connection and recovery is in chinese so not an option) on linux i have adb running so ubports installer can connect and if you use piggz script you can send device with adb reboot fastboot into propper mode
after flashing i am on 4.3.0.15 again test call and mobile network
enable dev tools / remote / untrusted and follow piggz instruction for waydroid:
https://www.piggz.co.uk/sites/pgz/blog/volla-manual-install
install storeman installer from store while you wait for waydroid image download 
a refresh i chum gui helps now and then when installation does nothing or no package found comes …
do NOT apply patches while downloading did that, not good
after reboot try out waydroid if it fails head to: https://github.com/sailfishos-open/waydroid for trouble shooting
i did option 1:
devel-su systemctl disable --now dnsmasq
devel-su systemctl restart dnsmasq
devel-su systemctl restart waydroid-container
test again waydroid , i had to reboot to be able to start it
then update using zypper. i am cautious so i did write down all the versions from 4.3.015 which is the initail os version if u use ubp, if you use script it is 4.2…
while zypper is running use the time to install f-droid, then aurora from f-droid
then install signal
install signal from openrepos
i did head again to windows as easyssh would not pass the whole register string … i used winscp for that following this instructions: Registration Workaround · Wiki · Whisperfish / Whisperfish - Signal on Sailfish OS · GitLab
and now i have a functional volla phone again - a piece of cake 