I'm using wordpress 4.9.6, and the max file size upload is now 8Mb. I used to upload 50+Mb video and audio, but it has changed. how can I change that to 100Mb?
It is something you can increase in your php.ini settings with your host server admin. I've found this resource for you: http://www.wpbeginner.com/wp-tutorials/how-to-increase-the-maximum-file-upload-size-in-wordpress/