Форум сообщества Firefox

I recently upgraded to the latest version of Firefox on my Macbook Air running 10.14.6. When I try to play embedded videos, the video will freeze and there is a message saying that it is slowing down the page. I am in another country with a 50mbs connection and have to use a different browser to watch embedded videos. How can I return to the last version of FF which worked?

I would like to make Firefox the default browser on my iMac but for some reason it refuses to load my home page on Facebook. I can get to the general Facebook page and login and see the news feed but when I try to go directly to my wall or home page, it gives me the message "This page isn't available right now. This may be because of a technical error that we're working to get fixed. Try reloading this page." I have tried clearing the cache to no avail. Anyone else have this issue or a possible solution?