I removed manually GmsCore.apk and GoogleServicesFramework.apk. The other packages were not there and i don’t have /system/product/priv-app directory. After that i was able to install ‘microG Services Core’ from f-droid.
But i have other problem. I installed Xposed Framework module FakeGApps for signature spoofing and it was installed successfully. But when i check if the signature spoofing is enabled, with Signature Spoofing Checker app i downloaded from f-droid, it shows that it is disabled. Why is that? What issues i could have if the signature spoofing is disabled? I think MicroG is installed correctly, because i was able to install apps like Signal and Insight Timer, which before i couldn’t install because they wouldn’t work without updating google service.