I can assure you that if you did it correctly, my method works.
The problem with using phpMyAdmin is you are limited by PHP's config (unless you tweak it)
My method is the best way to import a large SQL file.
It's the way I've been doing it for over a decade, and the way developers before me have been doing it since 1995.
If you don't know how to use CLI (you should learn) and must use a shitty interface such as phpMyAdmin, you'll have to edit your php.ini and increase at the least upload_max_filesize