A really strange situation after changing my mac's language

macOS & Mac Apps

Hello everyone!
Here I have an issue that I have no idea how to solve.
My native language is Russian and mainly I use my mac in it.
But I had to switch my mac to English.
When I switched it to English I turned off the auto loging in due to the security things.
After I switched my mac back to Russian I have these issues:
1. The most annoying issue that I don't know how to solve is that on a login screen Alex voice starts speaking everything until I login. I tried to find a way to solve this issue, change the voice in the login window, but if I change the voice in the login window the words such as button, table, list view and others are still pronounced by Alex.
I tried to uninstall him, it helped, but I need this voice on my system and I don't want to uninstall it just because it works in the login window.
It seems like we cannot choose the VoiceOver voice that is used on a login screen.
Is there a way how I can switch it to a Russian voice to work?
2. For some reason my calendar app practically fully became in English. It is not a problem but still I don't understand why it is in English when my mac is in Russian.
I don't have an Idea how to change it.
What can I do?
Especially I want to find a solution for the first problem because it really bothers me.
I have a MacBook air 2017 with macOs 10.15.4 Catalina installed.
Any help would be appreciated!
Thank you in advance!