MY FRIENDS! I DID IT!
It’s working:
const server = new Schema({
name: String,
icon: String,
owner: String,
settings: Array,
users: Array,
textChannels: Map,
voiceChannels: Map
});
await serverModel.updateOne({name: serverName}, {
$push: {[`textChannels.${channelName}.messages`]: message}
});

Damn it! I’m fkin the lord of the messages! Thanks a lot to all of you. I spent billion of hours to figure it out! All of you so helped me so much! THANKS A LOT FROM THE RUSSIA WITH LOVE!