first: Please tell us your system specs: OS version, Premiere version, amount of RAM, Hardware specs including graphics card
If Premiere was working properly before the update, I'd suggest you revert to the earlier functioning versions. If you deleted the previous version when doing the update (never a good idea), you can reinstall it using adobe creative cloud. At the far right of Premiere Pro in Creative Cloud there are 3 dots. If you click on them, you'll see the option for other versions.