bbPress.org

deprecated simply means it will throw a critical error in a future version, the screenshot you sent has loads of these for your theme and several plugins. These are warnings and should not precent your site working – you should of course switch off error display for your live site.

The critical error which is your issue will send an email to your admin account saying exactly what the error is – it is that we need to see

ok, so that error tells you it is a problem with the plugin gd-topic-polls

'call to undefined method xxxx in ...public_html/wp-content/plugins/gd-topic-polls'

That plugin is not written by bbpress and

GD Topic Polls: plugin for WordPress and bbPress Forums

says that the free version it is no longer being maintained.

There is a paid version at

https://www.dev4press.com/plugins/gd-topic-polls/

and if you have bought that version, then you need to raise a support ticket with them.

If you have the free version, then if you want to continue to use this plugin, you would need to buy the paid version