Installation and server related problems

Today I tried to upload my H5P course presentation 'Literary Criticism and the Scholarly Conversation' (https://h5p.org/node/410747) to our local WordPress site (https://www.cccc.edu/H5P/). I clicked on H5P content, Add New, and then tried to upload the file downloaded from https://h5p.org/node/410747. I recieved an error message that said 'Could not get posted H5P.' We are using WordPress 5.1 on a Desktop computer running Google Chrome.

I have a lot of anonymous traffic. That's why I integrated the Boost module (https://www.drupal.org/project/boost) into my Drupal-Installation. But i don't know, if the h5p-content will be cached, especially if other pages use the embed function.

Is there a possibility to get informations, how many h5p-contents are embedded on other sites?

Can i cache the h5p-content with the Boost module or in an other way?

I have installed H5P on my moodle server, everything is ok. my moodle system have two languages, english and vietnamese. all H5P editor UI and default texts are now in Eng.

How can I configure/translate the texts (I dont really need editor UI, but it also a need in future) to Vietnamese? I dont want my team have to repeatedly entry Vietnamese for text overrides for every h5p content.

Thanks.