Help. Macbook on catalina 10.15 beta now freezing and i cant log into app store to download mojave .

So in the past week since last update my macbook is freezing on me no matter what app i am using, safari, or just emails . I cant log into the app store either i can log into music but it keeps bouncing me back to the sign in box and then says error when i try log in. I need to get the app store to download mojave so i can go back as i cant have my mabook freezing a dozen times a day . without acess to appstore i feel a bit stuck.