log in problem between users

High Sierra: I put in my password and I never get past the first letter. Computer randomly starts filling out the field and I can't erase. The only way I can log on is to reboot. It appears the computer is giving me a language prompt since it starts showing me other languages in a search field as well. When it happens, computer slows waaaaayyyy down. We just upgraded to high sierra. Sierra worked just fine. Thanks