Cant delete messages or leave groups

I have an iPhone 7 Plus and Im going to have to delete this app because I cant, for the life of me, figure out how to delete messages or leave all the annoying groups people add me to. First of all it should be illegal to add someone to a group without their consent. Second it should be VERY CLEAR how to delete convos and leave groups.

TheHammerOfDoun about Messenger, v127.0