Issue with mail program, missing my groups in the adressbook

Hi all, I am having issue with my mail programm.Using Mac book air. I updated to mac OS Tahoe 26.1, also I installed duckduck go and got rid of my safari browser. Since then some of my mail addresses have disappeared and many only register the tel number but not the mail address. Also in my adress book ( german: Kontakte) the groups I had made have disappeared.

Anyone knows how I may proceed.