Blank screen when refreshing

Hi

Please can someone help me.

I updated the plugins earlier today. However I have just noticed that my wordpress website is now behaving rather slowly. Another major problem is that when I try to make changes and click the update button. I get a blank screen as opposed to page being refreshed.

Please can some one help me advise what is the best option. Is there anyway I can restore to a previous version. I noticed that I have a database backup plugin that has been running daily backups.

Please let me know thanks