Calendar and language problems

I have 2 problems with my theme. At first the problem is with the SEO Rank Math plugin, I even opened a ticket with them, but they asked me to show the error for you guys, because the problem may be the theme. See what happens when I activate Rank Math, the calendar changes formatting and I can not click it. When I deactivate the plugin it comes back.
The second problem is in Languages, in my case the site is in Brazilian Portuguese, but my dashboard is like this, I can not select the pt-br nor take the ENGLISH as default. I’ve already disabled all plugins, but it’s still the same. I’m sending the photos.