Could you try to log in to your site via FTP or CPanel, and delete the whole Jetpack plugin folder?
You’ll find the Jetpack plugin folder here:
wp-content
plugins
jetpack - DELETE THIS FOLDER
If you’re not sure how to do this, you can ask your hosting company for help. They should also have documentation explaining how to edit or remove files from your site using FTP or a File Manager in your admin panel.
Once you’ve done that, you’re welcome to give Jetpack another try. I would recommend going to Jetpack > Settings in your dashboard and activate each feature separately to figure out what’s slowing your site down. Once you find what’s causing the issue, let me know your site URL and I’ll take a closer look with you to try to understand what’s causing the issue on your site.
Let me know how it goes!