Final I found the solution.
Replace the Base URL from
CAUTION! The change is not allowed in magento2 admin.
I made it in MySQL in table cron_config_data and record with path='web/unsecure/base_url'. After cache:clean and varnish restart everything works smoothly in frontend.
Unfortunately problem remains in Backend. Magento2 redirects to this url:
This last problem solved by simply change the Admin base url from Stores -> Configuration -> Advanced -> Admin -> Custom Admin URL =