In most cases, installing a previous version will not help. Problems with an update are usually not caused by the new version of Firefox, but rather the update process. Installing a previous version doesn't fix most problems
Rather than downgrading, try getting used to the new features or ask a question on the support forum, to see if there is a workaround or a way to restore the old behavior without downgrading Firefox. If you dislike new features in the latest version of Firefox, your first reaction might be to go back to the previous version. Unwanted features in the new Firefox version
