How to get rid of duplicates in my telephone agenda? After installing Skype a week ago, my telephone agenda duplicated a lot of contacts, for many of them I have seven duplicates - therefore eight entries for each contact.

After installing WhatsApp, I had this problem too - many contacts had one duplicate.
But after installing Skype, the telephone agenda is a horrible mess. For each such contact, Skype added five or six more duplicated contacts.

I tried to delete one such duplicated contact and I got the message "This contact is read-only. It can't be deleted, but you can hide it." - and below this message I get the buttons "Hide" and "Delete", but I tried the "Delete" button and it works, so it actually can be deleted! Which is really inconsistent.

So the question is: how can I get rid of all those duplicate contacts? (without having to delete them manually, one by one, of course)

On other phones, you can access WhatsApp from the main contact, it doesn't have to be duplicated in order to send a WhatsApp message from the main telephone contacts list.

My phone is Honor 7s.

The Android version is 8.1.0

I am using the Nova Launcher but it acts the same with the Huawei Home launcher too.
in the contacts app, untick the "whatsapp, skype, etc.." from the "contacts to display" options, select "customize" and done!