Android 8.1.0? Telephone contacts double?

Short to the history:

I switched from a Nokia 6300 to a Huawei P20 and imported all contacts via the SimCard to my smartphone.

Now come to the annoying part:

After I installed WhatsApp all contacts are shown to me twice and to top it all, my Microsoft Exchange has added all the "email contacts", so maybe I even have 3 contacts to 1 person.

If I delete the SimCard entry, the entire contact is gone if I delete the contact with the WhatsApp icon, then the next reintabben is back… It's going to be crazy.

Have I overlooked a nasty backdoor somewhere that synchronizes everything over and over again, or does my smartphone just not like me?

No, that's what Android does. Do you have multiple apps that use contacts, all are displayed.

go into contacts> Top of the dots and then on "displayed contacts" because you just take the hook in "All contacts" out and put it in "phone" or "SIM" jeh after where the contacts are stored.

Saved my day, thanks